Celtics
For those wondering, you can aggregate players if you are over the 2nd apron, as long as you finish the trade under the 2nd apron. Celtics would have plenty of room under the 2nd apron to fill out the roster.
Starters:
White
Hauser
Tatum
Giannis
Porzingis
Bench:
PP
Scheierman
Horford
Kornet
Bucks
Bucks get draft picks and players they can either flip for more assets or keep in order to not completely tank. Rockets have had reported interest in Brown once upon a time, so I can see them trading assets and a young player if the Bucks were interested. Jrue can still defend, play-make, and shoot, which is valued on any team.
Nets
You can probably do this after the Nets us cap space elsewhere and trade Portis into the Full MLE. They are getting 2nd Round picks to take on expiring contracts, some of the 2nd Rounders are pretty decent too.