Seems like now would be appropriate for this: ISO Carnahan's MI Script.
To Cruise's credit, he is great at picking and developing scripts into successful films so if he had doubts, I'd imagine they probably weren't baseless.
“And we had flat-out the two best mask reveals in the franchise history. Like those mask pulls dealt with major plot stuff. They weren’t just these cartoony things.” - Carnahan on his script.
Lol, just makes me more curious about the damn thing. :'(