I think we'd have to give up an additional asset on top of Fox unfortunately, but I'd be more than happy to be wrong.
Williams is actually an interesting fit next to Sabonis with his size, length, athleticism, versatility, defense, and shooting potential, but I'd be surprised if McNair traded someone who could help him this season for someone who appears like they will be out for the rest of the season. It just doesn't coincide with his messaging.
You're right about the passing though. It would be interesting with those guys together on offense (although I still have my reservations about it defensively). In fact, this would be the AST:TO for all 5 of our starters:
PG - Mitchell = 3.31
SG - Haliburton = 3.23
SF - Barnes = 1.43
PF - Washington = 1.56
C - Sabonis = 1.57
That's pretty darn solid for an entire starting lineup.