Hawks

Collins for Smart + Juancho + 3 first rounders + 1 second rounder

Apparently, Collins is a little bit upset about his role with the Hawks and the Hawks desperately need some perimeter defense. Smart is a much cheaper addition than someone like Ben Simmons, while the Hawks can also add some draft assets to make further moves. Juancho's contract isn't guaranteed, so the Hawks actually save some money come next year. They could follow this up with Gallo + handful of picks for someone potentially decent.

Rockets

Wall + Bucks 1st for Horford + Nesmith + Langford

Rockets get off of Wall's contract, but it costs them a 1st rounder. To compensate, they get 2 young wings with some potential. Horford's contract next year is only partially guaranteed, so they save a boatload of money.

Celtics

Smart + Horford + Nesmith + Langford + Juancho + 2 first rounders + 1 second rounder for Wall + Collins

Celtics get their pass first point guard who isn't necessarily a defensive liability. They also get some shooting with size to pair with Timelord in the front-court. C's starting lineup:

1. John Wall

2. Jaylen Brown

3. Jayson Tatum

4. John Collins

5. Robert Williams

Overall

I think each team gets a little bit better fit. Hawks get sorely needed defense with future flexibility to continue to improve the team. Rockets get off of Wall's contract and get some ok-ish young pieces in return. C's get a better fit and more scoring/play-making without sacrificing too much on the defensive end.

Let me know what you think.