Yep, that'd be my choice too. I've said it to mates a few times, but, for some reason, they all seem to be against it. I honestly believe he would get 10+ goals if he gets rotated.
He seems like a totally different type of striker to Costa/Drogba so it could give defenders and managers something to think about if he comes on as a sub.
Edit: He wouldn't cost much either. As United's 4th striker he would be less then 10 million, which is quite cheap.