It's not a question of working or not for me. It's an speculation as good as any.
Bringing Michael back to fight AU Michael could work. I just don't see the time frame, but they can make up whatever reason they want for it. What I didn't see was the reason for Dean dying. Not a problem with that either. He'd be back in minutes too. I just don't see the point of killling him to bring him back so he can be Michael's vessel. Again too many things crammed in 42 min. but, once more, nothing new there either.
In fact I've never been against the idea of a possible Dean Michael. But there are so many loose ends that the closer we get to the end, the less clear I've got how they'll wrap it all in just one episode. That's all.
Thanks for taking the time to explain your theory.