About BG3 a single hotbar combined with "a button" to open your spellbook, a button to open your actions, a button to open your bonus action, a button for your consummables should be okay.
And this is the funniest part for me ...
We even allready have that button, its placed by minimap ... all we need from Larian is allow us to put in on hotbar ... and allow us to cast from there ...
And voila!
We will get allready implemented spellcasting interface that is bindable to hotkey, with all spells & sorted by spell levels.

With almost no additional work done.
