I could see this as a mod but not a game feature, if anything well probably get a create your own companion in act 2. That's if they keep to the divinity series feature.

I'd probably recruit Lakrissa or/and Nadira, could see Nadira being a rogue and Lakrissa being a ranger. Changing appearance wise would be a pass, not big on editing existing npcs.

Cool idea though, would be a nice replacement to the create your own that was in divinity.