You aren't going to like what I have to say...
Whilst it's true that I agree Miz should have been given more of a chance as WWE Champion, his reign failed to draw. In fact, the only thing drawing around this period was the return of The Rock. The main event of Wrestlemania 27 failed to promote any interest where Miz was concerned because all people cared about was The Rock and John Cena and whether they would have a confrontation.
I believe that the plan prior to The Rock agreeing to return was for an extended program between Miz and Cena that could possibly result in Miz having another title reign. As we know, this didn't happen, but I believe that it wouldn't have recieved that much more interest had it. The Miz is good wrestler, talker and personality, but he just didn't have the strength to carry a successful WWE Championship reign at that time. Could he do it now? Possibly, but only if he were placed in a program that the audience bought into.
I think that Miz should turn face and feud with Chris Jericho, this could be very interesting, given that both of them have made reality TV appearances and share similar character elements.