Spells like Shield and such things would be lovely. And booming blade! Yeah... stuff like that. Also, wizards should not be able to cast any spell from any class, as has been mentioned before.
I would love if they implemented a system like in Solasta for reactions, where you can choose if you want certain reactions as they present themselves in combat. Maybe slow down the action and a prompter comes up, like in Solasta? Also... many times reactions just don't trigger, does that have to do with character not standing close enough to enemies despite the fact that they should be in melee range? Maybe Larian needs to increase the reactivity radius or something?