I don't think Secret Wars would work. Too many conflicting characters and personalities to fit on the big screen at one time. It would be like Black Hawk Down in that you never get much emphasis on any one character and you'd walk out of the theater feeling rather unsatisfied. In BHD this is okay, because they are supposed to be just soldiers. But to have the XMen, FF, Spidey, et al, on screen at once all of which are recognizable characters and none having a significant amount of screentime simply due to the need to get the story told, would just be way too much in too little time.