Advanced classes? Not at the start of the game, but latter, unlocked via quests and, in some cases, filling requirements. Kinda sad that my ranger is actually thief. Then there could be hexblade/magic swordman, if character have certain skills from warrior&black mage classes as well as have done quest. Some sort of grey mage (black+white mage), could be fun too. Or maybe engineer/artificer class?
Ability to change background maybe? As you progress through the game. As you get fame and titles, your background also changes. You are no longer some noname adventurer, but a figure of renown.
Another problem (although could be wrong here, judging by what I have seen on wiki, since my first run is pure champion) is that there are very very few characters you can corrupt, if you are playing corrupted champion. If MC goes "demon" path, having ability to corrupt your companions&other npc is sort of essential? What's the point of being corrupted, aside being able "formally" pursue Kas (without tricks like running to give donations for good Pastor, so he remove your accomulated corruption)? Would love to see Brienne actually turned demon or Caith became so depraved that she renounce Mallach and start only worshipping your dick/pussy.