The V.A.T.S like thing they where going to use to hit monsters weak spot sounded cool, but it would be rather hard to implement.
1. - No AutoSheathing
2. - The ability to enter/leave combat state by drawing/sheathing sword
3. - A Sort Mutagens button
4. - This one's pure fantasy but since you asked: free running/mantling that allowed running up walls to clutch and climb, drop and hanging off ledges, etc.
Oh... and one more thing: NO LEVEL SCALING EVER! I hate that crap. In other words, the game is awesome. Just needs some fine tuning.
I feel that that is aplliable to any multplier in this series, oil have always made a negliable difference, atleast in this you can get superiour oils and all that but overall i think it would be better if those felt like they did more of an impact.mutagens and trophies are negligible for the most part
Unfuck Alchemy.
Unfuck enemy placement and encounter design.
Unfuck armor designs.
10/10
They really needs to improve the quest design, following trails with witcher senses and the quest journal, giving an option to disable the fucking quest markers.
It's really a bad Skyrim way to do an RPG.
That takes some effort, you need NPCs to give you good directions, which they do in some steps for the main quest, but sidequests are completely barren in this regard.
And this is something they should have done from the start.
Design the quests without quest markers, adding this option later.