Firstly, this is clearly a dream. I'm aware of that. And yet, since many dreams have a nugget of reality in them...
Boston trades:
Jared Sullinger
Tyler Zeller
Terry Rozier
David Lee
2016 Dallas 1st
2016 Celtics 1st
2016 Minnesota 1st (2016 and 2017 Minnesota 2nd if Minny doesn't improve a lot in standings)
2016 Miami Heat 2nd
$1.5 million in cash
Boston recieves:
Al Horford
Justice Winslow
Josh McRoberts
Shelvin Mack
Miami trades:
Justice Winslow
Josh McRoberts
Jarnell Stokes
Miami receives:
Jared Sullinger
Kent Bazemore
2016 Miami 2nd round pick
Atlanta trades:
Al Horford
Shelvin Mack
Kent Bazemore
Atlanta receives:
Tyler Zeller
Terry Rozier
David Lee
Jarnell Stokes
2016 Dallas 1st
2016 Celtics 1st
2016 Minnesota 1st (or more likely 2016 and 2017 2nds)
$1.5 million cash (makes trade payroll neutral for them.)
Why for Boston:
Pretty obvious, as they get two of their biggest trade targets.
Why for Miami:
This trade makes the better for this year. Sullinger is definitely better than McRoberts, and at least this season, Bazemore offers more than Winslow. Both are free agents, but their cap holds are pretty much a dead match for the salaries of McRoberts and Winslow. If they are able to resign both using their respective Bird and Early Bird rights, they would have a better team next year with the same amount of cap space. This trade also gets them completely under the luxury tax. They dump McRoberts, who still has two more years on his completely bust of a deal so far. The 2nd is a throw in that lets them potentially dump one more salary if they want to create a little more luxury tax space.
Why for Atlanta:
They get two firsts, two seconds, a promising prospect, and a useful big entering restricted free agency, whom they should very well be able to keep. (Stokes is a total throw-in to get Miami under the tax. He has no value). It gives them no long-term salary obligations, and, thanks to the cash from Boston, is payroll neutral. I included Rozier because I think he's the best of the rookies and James Young. The deal works the same with any of the others.
Why wouldn't Miam and Atlanta cut out Boston and just do a Horford-Winslow swap:
They could, but Miami seems pretty intent on not taking in any salary while they're in luxury tax territory, and so it's very hard to get them to match Horford's salary. They'd certainly have to include McRoberts, and they're pretty much out of picks and other assets aside from Winslow. Would Atlanta rather have $6 mil/year tied up to McRoberts to get Winslow, as opposed to more salary flexibility and multiple picks/prospects? Considering that they're looking at tearing down a lot of the team, I'd think they would choose the latter.
Anyway, this is a dream, but it's also a justification of why I've had crazier dreams.