Things I might like to see, if someone were working on an Infinity Engine style RPG:
More flexible loyalty systems.
By that I mean, if you're fighting an intelligent monster who is capable of communicating with you, you should be able to, in at least some cases, demand and receive their surrender. And they should be able to choose to stay loyal to you or betray you based on some complicated mechanics.
Infinity games already allowed you to temporarily snag monsters and put them in your party - Charm Person and related spells. However, when the spell wears off, the lone goblin, despite being completely surrounded and massively outgunned by your party, suddenly goes hostile again and fights to the death. Well, that's silly!
What if you could beat down enemies into a state of surrender, take all their valuables, and release them, transforming them from red hostiles to blue neutrals?
What if you could press-gang random neutral NPCs, turning them into temporary green party members?
What if temporary party members had a chance of making a run for it when near an exit (thus disappearing from your control) or suddenly turning hostile on you if they thought they had a chance?
Imagine: Your party is ambushed by a bunch of bandits. You fight them, and one badly-injured one cowers and begs for his life, offering his thieving skills to you. You let him come along and are able to use him to pick a nearby lock. If you exit the zone, you lose him, as he's done his job and it's assumed that you released him. If you stay in the zone with him, you notice that items in party inventory keep mysteriously ending up in HIS inventory, unless you succeed in spotting his pickpocket roll, in which case he goes hostile again... If you *sleep* in the zone with him, your party wakes up as he lands the Backstab Triple Damage Sneak Attack on the idiot who fell asleep by him...
Less-evil temporary party members might simply run away when you sleep. Perhaps in general, if a temporary party member gets far enough away from the rest of the party, they revert to neutral status and can no longer be commanded.
... And of course, a neutral who finds his way back to his still-hostile buddies might go hostile again and come back for revenge...