Obviously this is VERY unlikely but its fun to think about.
Bam and Spida next to Jimmy would be a win now move, and also brightens up the future of the heat franchise. After Lowry's contract expires the heat have a bit more breathing room to make some moves in the future to replace Jimmy Butler when he's done playing at this level.
The cavs would be making a lateral move in terms of their teams effectiveness, with Herro and Grant together shoring up the 3pt shooting leaving with donovan. In the same motion, they'd be getting a refund on the picks they spent for donovan. They can use their #18 pick to grab some backup front court depth in Dereck Lively, or a backup 2 guard.
Heat:
Spida/Caleb/Jimmy/Love/Bam
Cavs:
Garland/Herro/Grant/Mobley/Allen