Everything you suggested can be implemented in your game right now, by YOU. You have practically suggested to not save scum or revivify via items. You need a whole difficulty option for that? Just...do it.
-AI for party members (so the player doesn’t have to control them all)
I don't know what kind of self-harm you're into, but the AI in BG3 is very, very stupid. You're not going to get a true TT experience with this, you'll just get 3 baboons that intentionally kill themselves at any opportunity.