My ideal scenario is Rooney out too. Performances aside it makes my blood boil when I think about the 300k a week he's been stealing for 3 years. However, I saw some fire in Rooney's belly yesterday; first time in a long time. I have a sneaky feeling he may find some form for Mou.
I agree that Ibra, Roo, and Mata in the same line up would be lacking pace. They could rotate though. Might not be so bad if we played a front three of Martial, Ibra, and Griezmann. With Rooney and Mata as centre/attacking midfielders; Rooney tracking back (which he does do alot). With Schneiderlin playing a holding role. Still a bit slow but they would create a shipload of chances.