Dunno, and I'm not going to work on this
I guess you need to kinda copy the stuff from normal character doll to companion doll, + add all support for item equipped/unequipped.
Could be 1 few hours, could be a nightmare depening on what needs to be checke because of companion stuff working different then normal player doll.
Haven't looked into this yet but this would be a perfect idea for somone who seeks a new addon, or a beginner imo.