while i certainly wouldn't go out and hire karl as an AC right this minute, i think the notion that he would overshadow a head coach and refuse to take orders is a bit overblown. he has said publicly that he knows he won't join the coaching ranks as a HC and that he's ok helping the organization in WHATEVER capacity he can contribute.
there are plenty of superstar players who started as 3rd/4th assistants and were fine to quietly do their jobs outside of the limelight. one who came to mind is ewing. he was the main star of one of the most attention-getting franchises in the league for years, and then quietly transitioned to a seat on the bench where he has helped develop some of the league's young bigs. mchale's another guy who was an outspoken star in his day, then dabbled in TV, got an assistant VP job in a front office, then moved to GM, then coach, then back to TV, then coach.
i think karl would make a good assistant, once he gets to a point in life where he can commit to giving up his october through july again. hell knows we could use a big man coach who actually knows what it's like to be a big man. (the main reason i'm not excited about the livingston rumor.)