Instead of adding another difficulty (which would be pointless if AI wouldn't be significantly improved) just add a more realistic option where resources would be scarce (potions and scrolls), we wouldn't be able to rest as often and saves would also be limited to camp sites only + the moment we would turn the game off. That way most of the broken builds would be nullified (e.g. wizards wouldn't be as powerful, fighters wouldn't be as invulnerable, etc.). Oh, and get rid of all he junk and empty containers while you're at it.
Anyway, Larian games were never that difficult. If you want to play good challenging RPGs play Colony Ship, Age of Decadence, Jagged Alliance 2 (and 3).
