Assuming WB owns the rights to Midway characters/franchises other than MK, I feel some of them could be reintroduced in the MK franchise. I'm not suggesting any non-MK Midway characters as guests, but to make some of them part of the MK franchise, tweaking them a bit in order to incorporate them in MK's story.

I'm especially thinking of Mace: the dark age. It would be a shame for some of it's characters such as Lord Deimos, Sir Dregan and Grendal not to ever appear in another game again. I certainly wouldn't be opposed to a new Mace game, but I'd still like to have these characters as an actual part of the MK franchise. Maybe some War Gods characters too.

I think it could open up interesting possibilities, both when it comes to story and gameplay.