Is it just me, or does WWE have the whole "stunt double" angle backwards? Shouldn't Miz want to use the stunt double to do the bulk of the wrestling for him, and just come in at the end to claim the glory of a win? It would make sense that he is protecting his Hollywood image by not putting himself in harm's way.
It would also take away the issue you pointed out that these matches suffer because they require Miz to work basically the whole time by himself. You could structure the match in a way so that you still get the funny Mizdow antics (Miz starts out each match while Mizdow mugs outside, Miz tags out fairly quickly after taking any damage and thinking it's better to keep safe and let his stunt double take the brunt of the punishment, Mizdow works the match and then Miz tags in for the selfish pin).
Kudos on the Radioactive Man reference in the title. And yes, this is EXACTLY what they should be doing with it, and it's kind of how the angle started. It actually makes Miz look like kind of a badass to be facing two guys at once while his stunt double acts like a clown on the apron, so why do it? This version would work more if Miz was a babyface who was determined to fight alone and Mizdow just kept bugging him like Steve Austin and Dude Love. I mean, they can still redeem this by having Miz finally accept his stunt double as a partner, but I don't feel like that's where it's going.