Lee Cummard coming home early created problems for the program in the form of a scholarship crunch, he didn't come home because BYU needed him.
Max played for ASU and while he was a great QB for BYU, it wasn't clear that his coming home met a critical need. In fact, if he'd stayed out his whole mission, he still would have been able to play in 2007 because this was before the Riley Nelson rule.
No, I don't think there are a lot of examples of guys who come home just when they are needed by BYU. This idea is a fantasy of USU fans...and apparently some BYU fans too.