I think the flex is interesting in WIS, it is a more perimeter orientated offense. Im no expert, but I've been researching different approaches to flex. Personally, as long as I have one player with a strong low post, usually my center, then I'll feel set. And then fill out the rest of the roster with three guards and a SF/PF.
I personally like having Ball handling as well in the flex with my good passers, think of double penetration.