I know this won't happen, but it's still fun to think about.
They have a perfect opportunity for an old movie in the 4:3 aspect ratio. They are already going with several casts, and it looks like the two primary casts will have their own theaters. For the Joel episode they could have the original SOL with the 4:3 theater. An alternate universe SOL that Joel never escaped from somehow pops into the current MST3K timeline. Fun ensues.