You're talking about the potential difference between the 8th-14th and the 1-5th picks, here. Hayward is not worth that and Milwaukee would laugh at the proposal just to swap.
If the Jazz make that trade, then they likely wouldn't end up trading picks. As bad as Hayward has been shooting at times this season, he still makes the team better. So does Marvin Williams. They both go to Milwaukee, they might make a playoff push in the east, and the Jazz are back in tank mode. We would need their pick straight up or their pick next year.