I’ve always said that D4 Paladin’s unique class mechanic could very well be: “Oaths”
As in DnD, you take an oath (which is kind of synonymous with Paladin lore) and you branch into a discrete subclass.
Regarding Wizard:
I know this will never ever happen, but Iwould have the Wizard of D4 take inspiration from Dota’s Invoker. Basically you have to learn this class- input codes of 3 elements to conjure utility spells.
There is a distinction between Sorc and Wizard here.
For the Wizard I envision a hot bar that can host 20 spells depending on the quick code input by the player- and is rooted in leylines and incantations, long term spells and utility skills like suspending the party to avoid boss mechanics.
OBVIOUSLY this is not everyone’s cup of tea, but Invoker is incredibly popular in the hero roster, for how hard he is to play, even though he is nuke-focused.
A Wizard being more quirky and utility-focused would be a dealbreaker for many players