He'd at least have to make a M:I that makes Marvel tyoe money. Sure the films are critical hits, but they are still relatively modest box office success stories when you look at how big the budget are for the films. He'd have to break $100 million opening weekend to get that kind of freedom. And even then, it's rare. It took the Russo brothers 3 films to get there (Winter Soldier, Civil War, and Infinity War). I would say they only now have the ability to make what they really want to.