Hello there and welcome to my small list of things I would love to see added to the game of Warcraft feel free to share if you agree and add things yourself that you would love to see added to the game.
Customization:
Class Specific Customization: While Shadowlands is focusing on adding more customization to all the races which is great I would love if Blizzard in the future go deeper into the classes and add customization to specific classes similar to how Demon Hunters have their own specific customization.
So for druids for example could be antlers and stuff inspired by Malfurion while Paladins could use light glowing eyes based on Turalyon and things could just get wildly explored here for what anyone deem fitting to the different classes theme.
Druids:
Would love to see all the Form models updated to Kul Tiran / Zandalari Troll quality and would be nice to see more colors added as well while at it.
Could also be awesome if the Treant form was updated as well with some color options added.
Possible forms from the past that could be added as well such as:
Druids of the Flame Scorpion as Bear Form.
https://i.ytimg.com/vi/qzoKnuaOnYw/maxresdefault.jpg
Void Elf:
Make it possible with a glyph or something to disable the void effect from the proc for those who wish to play proper ‘‘High Elf’’ feeling.
Face Tattoos similar to Alleria and as seen for High Elves in WC2 overall I think it was?
Some examples found through another discussion thread.
https://i.imgur.com/5TdYJTa.jpg
Orcs:
Non-Spikey Fel Orc Skin
https://www.wowhead.com/npc=42301/horde-portal-sentry#screenshots:id=447744
The following skins I believe are:
Dragonmaw, Blackrock and Fel Orc
https://i.redd.it/ugmppztosmv41.png
Gnome & Mecha-Gnome: Leper Gnome Skin Option!
Example.
https://i.imgur.com/l0v0Uoi.png
Forsaken: High Elf ears since big portion of the Scourge population was also added through the destruction of Quel’thalas!
Example.
https://i.redd.it/9dk7h7pbuz551.jpg
Upright Option for Forsaken as seen at Dazar’alor in BfA.
Example.
https://i.redd.it/59gppryvwas41.png
Death Knight:
Cult of the Damned face tattoos like Thassarian.
https://www.wowhead.com/npc=93456/thassarian#screenshots
More Undead ish skin options for Pandaren and the Allied Races Death Knights.
Weapons:
Gorehowl WoD Edition.
https://i.gyazo.com/2bf80e9afa97691aafbc74325a246fec.png
Either update Karazhan one (which I prefer not) or make it a quest chain that involves trying to discover what happened to Grom at the end of Mag’har Allied Race quest or allow it to be a quest where the Lightbound try to invade Azeroth and one of the ‘‘elites’’ wields it and drops it once killed.
Armor:
Grunt Helmet: It is such a shame that when they added the Grunt set back in WoD that they forgot to give us the helmet so please lets finish this set once and for all!
NPC Example.
https://wow.zamimg.com/uploads/screenshots/normal/438897-warspear-grunt.jpg
Stormwind Soldier BfA: This recolor was never added through Warfront / Outdoot Arathi Highlands content which is saddened as I would love this set on my Human Warrior specificly due to Stormwind Soldier using this set.
Would be great to see it somehow added to the game for us who wish to transmog ourselves into Soldiers of Stormwind!
Picture of the set
https://i.ytimg.com/vi/BKj__TFmY-M/maxresdefault.jpg
WoD Stormwind Set Recolors:
Would been awesome if they added something similar to these recolors to the game and the Seven Kingdoms tabards.
Picture example.
https://images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com/f/f274f03f-58ff-446b-8444-e6093648b302/d9wfpmv-6cd2c8cc-bcd9-46d2-b47a-641a4c3bd56a.png/v1/fill/w_1343,h_595,strp/the_seven_human_kingdoms_of_warcraft_by_miloscub_d9wfpmv-pre.png?token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1cm46YXBwOiIsImlzcyI6InVybjphcHA6Iiwib2JqIjpbW3siaGVpZ2h0IjoiPD04NDEiLCJwYXRoIjoiXC9mXC9mMjc0ZjAzZi01OGZmLTQ0NmItODQ0NC1lNjA5MzY0OGIzMDJcL2Q5d2ZwbXYtNmNkMmM4Y2MtYmNkOS00NmQyLWI0N2EtNjQxYTRjM2JkNTZhLnBuZyIsIndpZHRoIjoiPD0xODk4In1dXSwiYXVkIjpbInVybjpzZXJ2aWNlOmltYWdlLm9wZXJhdGlvbnMiXX0.d2dhs1Hr5x3rhCS3s07HCXz757PDL8P99PA0iW1oh1g
Frostwolf Garb: The set should be extended to at least mail as it makes sense for hunters to be able to use this set.
If not it would be nice to see all the WoD sets extended to be free of armor restrictions to allow more customization specially for Horde characters.
Example of the Frostwolf Garb.
https://i.redd.it/3s4naqojwqc11.jpg
Allied Races:
I would love to see Allied Races weapons to be added and also the other two recolors of the set added too similar to how Mag’har Orc did receive three different colors.
Video of Nightborne and Void Elf Weapons.
https://www.youtube.com/watch?v=3h2DfsYfGyc
Same with normal races heritage weapons too.
Blood Elf example:
https://wow.zamimg.com/uploads/screenshots/normal/808985-silvermoon-city-guardian.jpg
Mecha-Gnomes specificly is quite desired because the different heritage armor fits them when it comes to the color of their robotic customization so I would love it to be added specially for them.
https://i.imgur.com/uzj5rUn.png
Mounts:
Non-Armored Horses: Would love to see all the old non-armored horses to be updated to the quality of the new horses as seen done with the Gilnean ones and Kodos is another example where they been updated as well.
The Four Horsemen Steeds: Either for Death Knights only or for everyone to give more customization when it comes to undead horses.
Picture of the four horses. Grey, Green, Red and White.
https://gamepedia.cursecdn.com/wowpedia/3/36/New_Four_Horsemen.png
Overall I think it is good if Blizzard put some time and energy into start to slowly update the older mounts small batch of them with each coming patch until they are all updated while adding new and exciting mounts to come as well.
Class Mounts: Human Paladin, Blood Elf Paladin and Death Knight Class Mounts should be updated as the other races gotten unique and updated mounts.
Shaman Ghost Form: Should add customization to represent the different Shaman races better.
Wolf suits orcs just fine while the Raptor fits trolls better and I could see Kul Tiran maybe have something more themed after Kul Tiras and the options just carries away!
Locations:
Brennadam: Would love to see some type of quest where you can phase out Brennadam to make it ‘‘repaired’’ as it is one of the major locations available in Stormsong Valley that should be accessible to the players.
Example of Brennadam before the Horde invaded, such a lovely place.
https://gamepedia.cursecdn.com/wowpedia/e/eb/Brennadam_Square_2.jpg
Garrison Harbor: Garrison Harbor is another excellent location that could be used but sadly due to how phasing works you can’t be there with your party friends so if that could be fixed that would be great too!
How the Garrison Docks looks like.
Alliance: https://wow.zamimg.com/uploads/screenshots/normal/472229.jpg
Horde: https://bnetcmsus-a.akamaihd.net/cms/content_folder_media/3WRHIMK75WD71433278387987.jpg
Race & Class Combos:
Worgen and Goblin Monk: They should been added long time ago because monks is such a class that is teachable to all races through studies in the Chi.
Human: I would like to see Druid and Shaman to be added for those who wish to play as non-fat Kul Tiran and make closer connection between Kul Tiras and the rest of the humans.
Dwarves: With Wildhammer Dwarves added there been interesting discussion regarding if they have druids or not. Sadly it used to be part of the RPG so it is no longer canon but a fun thought nonetheless if Blizzard wish to pick it up again.
Draenei: After meeting the Rangari in Warlords of Draenor I always felt like Rogue should be available to them.
Orc: Priest same as the Mag’har due to the Shadowmoon Clan.
Allied Races:
Void Elf: Paladin. Mainly due to High Elf theme but can be tricky due to High Elves being same race as Void Elf.
Kul Tiran: Paladin should be available.
Highmountain Tauren: Paladin and Priest, they should also be able to praise An’she and gain access to the light through the sun like their regular Tauren friends.
Lightforged Draenei: Monk same as with Worgen and Goblin it should be accessible to all races due to how it is taught by the Pandaren to everyone interested in it.
I personally would’ve loved HMT Warlock due to Feltotem but I understand that is more a taboo thing to practise so I understand it wont be added.
Zandalari Troll: Warlock I could see added now that they are more integrated part of the Horde.
New Races or added as ‘‘Sub Race’’:
Trolls of all tribes: Jungle, Forest, Sand and Ice Trolls customization available as they have different sizes to them would be great to see in the future when Blizzard feel like they have time and effort to see them playable.
Example for Forest, Sand and Ice Trolls.
https://wow.gamepedia.com/Council_of_Elders
Broken Draenei: With Legion we got high quality Broken in Argus that would be a great addition added to the playable race pool, could see the Outland ones updated and added as well.
Argus.
https://pbs.twimg.com/media/DE9DQ8RUMAAbu0F.jpg
Outlands.
https://gamepedia.cursecdn.com/wowpedia/9/9e/Nobundo_Legion.jpg
Ogre: They have been part of the new Horde since Warcraft with Rexxar taking over the clan during the founding of Orgrimmar and it would be great to see them playable for the Horde with the option to choose between one or two heads with fitting name for them as well such as Cho’gall & Dagg’um based on they have two heads.
Mok’nathal: With Rexxar being such honored person within the Horde and Mok’nathal have quite some healthy population in Blade’s Edge Mountains and their cooperation with the Horde during TBC it would be cool to see this race added into the Horde as playable.
Rexxar’s New Model as example.
https://i.imgur.com/T6trrBS.png
Beastmaster in Warcraft 3 Reforged.
https://wow.zamimg.com/uploads/screenshots/normal/880912.jpg?maxWidth=2400
Hozen: Hozen joined the Horde during Mists of Pandaria and later seen in Dazar’alor as well as part of the Kor’kron. They would be a excellent race added in the future.
Picture example from BfA Dazar’alor.
https://i.imgur.com/D96MF3p.jpg
Taunka: Taunka joined the Horde during WotLK in the war against the Lich King and make sense that they should be added as customization over time. They could be easily added as face option for Tauren or it would be nicer if they did get some more of ‘‘sub race’’ option instead.
Example.
https://vignette.wikia.nocookie.net/wowwiki/images/9/9e/Taunkamnxsuu1.jpg/revision/latest?cb=20080722021843
Yaungol: While they were never introduced into the Horde and remained hostile to both factions during Mists of Pandaria it would be cool to see them introduced into the Tauren society as we later through Chronicles found out that the Yaungol is the original shape of the Tauren.
Example.
https://media.mmo-champion.com/images/news/2012/march/yaunkas.jpg
Jinyu/Ankoan: They are races from same ‘‘type’’ similar to Broken. Jinju remained on land while the Ankoan went to the sea long time ago.
They could be a possible race for the Alliance as they have ties with them both in Pandaria but also Nazjatar zone.
Jinyu.
https://media.mmo-champion.com/images/news/2012/march/jinyu_recolors.jpg
Ankoan.
https://media.mmo-champion.com/images/news/2019/april/ankoan.jpg
Gilgoblin: They were allied with the Horde during Nazjatar zone and could potentially be added to the ranks of the Horde as their model pretty much is recolor of the Goblin one.
Male.
https://static.icy-veins.com/forum-files/uploads/monthly_2019_07/screenshot_118.jpg.a2eafd555f05c1ae1e6d6ef93a6b1d9e.jpg
Female.
https://static.icy-veins.com/forum-files/uploads/monthly_2019_07/screenshot_123.jpg.4dce3af122215ef10f53ba4e720cc677.jpg
Vrykul: Vrykul is another race that could be cool seeing playable as we have both fought them and aided them throughout WoW’s history.
Male.
https://gamepedia.cursecdn.com/wowpedia/d/de/Dragonflayer_Berserker.jpg
Female.
https://wow.zamimg.com/uploads/screenshots/normal/497322.jpg
Mogu: Another popular race that many like. Both been hostile and allied in 8.3 with Rajani.
Male.
https://gamepedia.cursecdn.com/wowpedia/3/3c/Zhang_Ku.jpg
Female.
https://gamepedia.cursecdn.com/wowpedia/9/9c/General_Xing.jpg
Miscellaneous:
Tents: Add Tents back into the game which was available in WoD through Leatherworking I believe it was? It was such a nice thing to be able to put down and I see little harm adding it back to the game.
Black Market Auction House: Revamp the BMAH so you remove all the old gear and recipe pieces from Mists of Pandaria that is pretty useless these days and keep it only for rare or unobtainable things such as mounts, toys and transmog.
I find BMAH a great way to keep things in the game after being removed from world events such as the Core Hound mount from Anniversary event or example the Plague Proto-Drake from Naxxramas 25 raiding achievement (Black still not available though from the 10man version 
)
It is a great way to get rid of gold and let things still be obtainable after it been removed / being a low drop chance from specific content.
Death Gate: Make it possible for higher level Death Knights when they click on their Death Gate to get the option to teleport to Broken Shore Acherus or Eastern Plaguelands Acherus as it would make it easier to travel as a DK as a nice perk.
I am going to update this thread over time as I discover more things I would love to see added and please do not hesitate to share stuff you wish to be added too by posting it here either with pictures or just explain what it is you wish to be added.