KY seems to subscribe to more of a positionless basketball philosophy, and I think we will see a wide variety of personnel together in sets that CB will probably find unusual. However, with KY's emphasis on shooting, that does seem to push Fous and Keba (and to a lesser degree Mag) into much more defined roles.
Fous doesn't have the slashing ability of Keba or Mag. If we end up running a 4.5 out scheme, Fous' current game is probably going to force him into a dedicated 5 role coming off the bench where he'll be more free to dominate the ball on the block without taking too many touches from Hall, Demin, Baker, Catchings, etc. If Fous adds an outside shot (which I assume is what Fous means if he said he wants to play significant minutes at the 4), that means we can maybe run something closer to a true 5 out rather than the 4.5 that most people are assuming. That opens up a world of interesting possibilities. If Fous can pull that off, it's a win for everyone.