OK here are some things i thought of that could/ could not be taken into consideration by the devs.
Tradeing should be left free as in no restrictions (its not wow diablo never had bind on pickup) its a stupid thing to add and it creates chaos.
It messes with the tradeing system. People like to trade top tier items and make good currency of those and buy other high endgame items to min max there characters. Its a never ending circle. Items anyhow need to be grinded they dont fall from the sky anymore or so they sed.There could be some special items what drop like from world bosses or a specific boss what diversifies the end game besides dungeons and whathever you have in mind. Idea is item prices will fix themselfs in time and a oveerflow in some form of currency or a otherwill always exist but this is where point 2 comes in.
Adding new legendaryes/nerfing others is a good thing its ballance change and helps the game allot evan the trade mentioned in point 1.
Heres how i see it: Il give a lame example the stone of jordan ring witch gives + 1 to all skills lets say this whould be a sought off items and very expencive what if in season 2 you ballance it like this ‘’+ 1 to all skill lvls for X seaconds if Y condition is met’’ activly nerfing the ring and ballancing it at the same time. Might be good for some builds might be bad for others but it crerates diversity and in its stead a other item whould take its place as high market sell point. Ballancing evrey season as it comes around by the new items/gear themes that are introduced. You dont need to make it like this but its a example of what you can play around with to make meta builds new and interesting evrey season.Nerf a build create a other. dont need to add damage numbers to skills and tallents and multiplyers over multiplyers like Diablo 3 had that effectivly ruined the game you just have to tweek the items allready existing in the game and in some case add somthing new.
Point 3 Level of the game
Level of the game should be 100 and not that easy achiveble simple as that
Point 4.Legendary items
From what i heard legenday items will drop the same for diferent lvls so youl get the same legendary item over and over again as you lvl and farm. Thats a mistake
The legendary system should progres whit your lvl but insted of geting that item over and over again you should drop higher lvl more powerfull items as the game progresses. If you realy like a low lvl legendary you could implement a artisan or some system that raises the lvl of a item at a cost. Droping the same thing over and over again its repetitive and becomes boaring.It whould become a loot hunt for + 1 stat for evrey item equiped what frakly whould kill the game in the end.Its ok to get duplicate items as long as they are the same tier lvl not one from starting the game and one in end game but with diferent stats . Thats just lazy in my opinion.
Point 5 End game
So in this years blizzcon they presented 1 form of the end game trough dungeons (they sound more like poe map system than rifts but call them what you will) Idea is that as long as that key holds more than just 1 affix it becomes interesting. The more dangerous the better and the higher value
A other form of end game content is to farm some sort of uber versions of the bosses. other is world bosses theres potential there
Final point Crafting:
Crafting in diablo games never had a sweet spot lets be real. Diablo 2 had a easy level starting system called INBUE and that was it there was some crafting trough runewords and gems but i could hardly call that crafting.
Diablo 3 had the worse crafting i ever seen . none of the items you crafted where basicly ussable at end game.
Crafting is based more or less on creating your own items with the stats you like/need at a cost. So if rare items are not to become a thing in diablo 4 i realy see no need for crafting.Legendary/set/mythic items have fix stats and thats how it should be but rare items have potential if given enough concern.
I dont know if eny developer sees this or even if theyl take this in consideration but evrey bit helps and i hope feedback from the comunity whould be accnoleged this time around