Remove affixes. Bosses/mobs Hp and damage increase each level
Keep seasonal affix, that is fun and useful.
Remove timer.
Give loot scaling according to the difficulty, with +20 loot being on par with mythic raiding.
Deserter debuff if you leave dungeon.
No keys, just a menu when you click on the pedestal showing the different level you can choose (with the highest being your best completed run + 1)
I’m going to assume you didn’t read my above post, because when I said a more robust scoring system I actually included timing as one of the things you would be graded on, but included other factors to be graded on that could make up the difference in score if you didn’t make a timer. You wouldn’t have a perfect score but you still wouldn’t have a binary win/loss based on making the timer or not.
The timer being off-putting is the issue to myself and my friends but we recognise that it’s a theoretically endless scaling difficulty challenge mode so time should matter and not be the be-all and end-all. Otherwise why not just lock gear to a certain level, enemy stats to a certain point and go back to the old MoP challenge mode structure?
I had an idea about legion tw bringing back legion m+ dungeons in the pool
-First thing first : I’d remove aoe cap all together
-Secondly, I’d go with class uniformisation in terms of utility. I’m sorry, but I’d rather be a mage or a moonkin than being a ret paladin in M+
-Thirdly, I’d make some trashs packs less harsh to deal with
-Lastly, I’d make key free, ie you have a 15 key, you can run what ever dungeon you want instead of being forced to clean a dungeon you may dislike
Interesting; how would you incentivise people to go for the less popular dungeons? We know that there are some dungeons that people avoid like the plague and some that are comparatively easier?
Would you even want to offer an incentive to go to these dungeons?
Unpopular dungeons are unpopular because they kinda sucks. So it’s on Blizzard to fix what ain’t right within those dungeons.
Or better : I’d add dungeons from previous expansion within new season rotation.
Balance the affixes so they equally punish melee and ranged
Ooooh that’s an interesting idea. Imagine a rotating season of different dungeons from past and present expansions. Would be a nightmare to implement at first, I think, but could really shake things up!
I’m not entirely convinced Blizzard can make a dungeon un-suck though. Seems to me their idea is “if people don’t like it just tweak the numbers until it’s a steamroll and the numbers go up.”
remove stupid affixes like necrotic inspired, these dot crap affixes and basically all affixes are boring 
Remove aoe cap problem solved
I disagree with most of what you ask for. Specially the key removal, no thanks. I can see it looking fun but working out terrible.
As for positive affixes, yes, I have long advocated for these. It’s VERY hard to balance though and I can see it becoming rather dull. Tyrannical/Fortified aren’t super fun but they do work in the sense that people try to push way more on Fortified weeks, creating a positive thing out of a negative one (negative being Tyrannical).
Perhaps a stacking dmg buff during the instance as you kill things could be a thing I guess, which would reset on deaths.
We DO need a lot more instances though. 8 is downright anemic and the 10 we’ll have in a YEAR is the same amount we had at the start of BfA, which was already low.
Aight.
Insta invites to any party. All other key holders MUST invite me or risk a ban.
Nothing else pretty much.
Oh…and get rid of big bad rio. 
Get rid of spiteful and storming as they unfairly penalise melee. Change sanguine to also silence anyone within it so moving casters out doesn’t need LOS or a class that can move the mobs.
If you still have to run all dungeons to up your score, I don’t see the issue with this system. Can you elaborate?
The timer is quite harmless. Failing to time a run only results in a minor ilvl reduction of 1 of the rewarded items. And RIO gives a lower score. But that is it.
The weekly affixes make the dungeons more fun overall. Yes, they feel annoying at first, but when you learn how to deal with them, it’s doable. Except the one that boosts bosses - I hate that one.
Keys are also good as it forces players to play all dungeons, rather than only Freehold or Mists.
Bringing old dungeons into the mix is definitely something that would be cool. I know that other games such as Counter-Strike or Heroes of the Storm rotate the map set every season in competitive modes to keep the game interesting.
Instead of getting rid of melee punishing affixes, they just need to balance out ranged and melee punishing affixes and alternate them every week. At the moment, only quaking is clear cut caster punishing affix tho
Just cut casters damage by half and is fixed.
They don’t do the afixed but they don’t do damage either so is good
I agree with Shihiroki on this one, if players don’t want to run certain dungeons, means those dungeons suck design-wise and should be looked at by Blizzard
Personally I dont enjoy Mists, much prefer Sangine Depthc, go figure.
My first big impression when I started doing m+ in SL is that I would definitely not enjoy being a melee player due to how affixes work.