Guys function in that role all the time (Alvin Gentry, Maurice Cheeks, Brian Shaw, Phil Johnson, the list goes on forever). I don't think it's a binary thing, or that a path is unidirectional.
I'd welcome him back if Igor bounces and I think such a thing would make a ton of sense for everybody. Outside of Igor leaving, I don't think it makes sense for Jeff.
That Suns season wasn't an accident, and say what you want about LHM, the guy had an eye for finding people as he had full faith in Hornacek as a coach (and made his statements without any apparent external or ulterior motivation). Dude knows the game, maybe he's just a mediocre head coach and got dealt some ****** situations and achieved how most coaches would given the circumstances.
I also think tradition is cool (a bonus, not a primary motivator).