This move actually makes good sense to me. You trade out some of the glut of PF/SF for a guy you might use at SG. I know people like Acy, but the guy was never going to play. So we bring in Ellington, see if he can make the roster and contribute some shooting (and a good insurance in case Ben/Nik is a failure). And it costs us nothing. We don't give up our expirings (Ellington is also an expiring), so we still have the ability to trade an "ender." Plus we pick up a second rounder. It isn't earth-shattering, but it is logical. I mean, doesn't one roster look much more balanced than the other when you compare:
Cuz/JT
Evans/Landry/Moreland
Gay/DWill/Caspi
Nik/Ben/Ellington
Collison/Ray
OR
Cuz/JT
Evans/Landry/Acy/Moreland
Gay/Dwill/Caspi/Outlaw
Nik/Ben
Collison/Ray