I've been saying for a while now....
Why doesn't Wade for Dwight, straight-up, work for both teams?
It'd be one of the biggest trades of all time. It's not likely, I get that. It's predicated on Dwight's back injury getting better (yes, a dicey proposition). It requires Dwight to accept being the #2 guy on a team.
Miami would lose one of the best players in the game, but would get back someone who's even more valuable when healthy. No more concerns about the frontcourt. Bosh/Howard would be an epically strong frontcourt. Bosh can keep playing the midrange, while Dwight plays down low. No more duplication of skills with LeBron and Wade; it's LeBron's show.
For Orlando, while they might want cap space, what they need even more desperately is to stay relevant and be able to sell tickets. They aren't in a particularly strong market, they can't really futz around with a full rebuild and a half-full arena. They still have a HUGE amount of salary commitments (Otis Smith really made some dumb, dumb deals), and I don't get the sense that they can go through a couple years of half-full arena while they rebuild.
Bring in Wade, you're selling tickets.
What better return could they possible get for trading Dwight Howard? Nobody they could get from Brooklyn is going to cause season ticket sales to go up. A guy like Andrew Bynum - the same. Good player to have, not someone you necessarily pay up to go see. You need stars.
I don't know why the trade doesn't work that simply. Maybe send over Jameer Nelson so Miami has a (slightly) better point guard, or maybe get Miami to take on Baby Davis in exchange for Haslem (Baby Davis would probably help out Miami quite a bit).