First off, Flip is not coming as GM with RA still as coach. RA is calling the personal shots Taylor has a little input (thankful, or Derrick Williams would not be a Twolve) and Kahn has almost none (Kahn is expected to do the work based on RAs desires for talent while maintaining budget). There is no need for Flip nor any meaningful role in this arrangement. And as best as I can tell, Taylor is OK with this arrangement and I would expect Kahn to get a contract extension equal to what RA has left on his contract.
There is, however, some legitimate concern as to if RA will remain as coach. If RA decides to retire to care for his wife, then the Twolves will reset including a new GM as Kahn will not be retained. No inside knowledge but I suspect part of what Flip gives to Taylor (besides another set of eyes on current league issues) is lots of solid contacts in the NBA. Flip is very well respected. (Hopefully, this helps Taylor as Taylors complete lack of contacts was part of the downfall in the failed GM search that resulting in Kahns hiring)
By the way, Flip left based on McHales decision that the players had tuned him out. I always felt that was unfair Sam and Latrell were totally tuned out well before the season started it was not going to matter who the coach was.
Flip was always a professional and managed the players as if, they too, were professionals. That worked when Flip had really strong, professional players. But Flip has never seemed comfortable taking on the dominating personalities (KG in his later years here, Ben Wallace in Detroit, Gilbert Arenas in Washington as examples) and that has been his coaching downfall. As an offensive tactician, Flip is still considered by many to be a top mind. So, comments about Flip not being able to coach in todays NBA offensive schemes are very misplaced.
Could Flip be a good GM? Who knows. But he has worked in 3 different organizations, is a smart guy, has some great relationships, and has shown ability to work with a wide range of talent. He is far more analytical than McHale and somewhat less loyal. I would see him as a significant upgrade to Kahn. Plus, I would not be too worried about the return of too many ex Twloves assistants. I think Flip has learned from that in Washington.
Finally, my perspective on Flip could be colored a bit by the fact that I got to know him a bit when he (and my) son(s) were in AAU at the same time many years ago. He is a very down to earth guy and I have always wished him the best.