I want Motaro in, but they killed him off in MK9.
If he comes to MK10, though, I hope he's 4-legged and not that 2-legged centaur bullshit.
Either Goro or Kintaro can also come back as Sub-Bosses or in the Sub-Boss rotation, since technically they didn't die in MK9.
The main baddies should definitely be Shinnok and Quan Chi (with Quan Chi being playable, since he was playable in MK9).
Shinnok should be the hard, non-playable final boss for MK10, to make up for the crappy Shinnok that we got in MK4.