In all honesty I'd like to see Liu Kang as a SubBoss.

No. He seriously overstayed his welcome. Unless they do something original with his story, I don't want him back. At least for this game.

Id like to see Motaro

i liked Goro and Kintaro in MK9

Belokk anyone? I mean,everyone seem to want some big subboss.

If not him,I want them to make Drahmin as sub-boss. Storywise,since Drahmin is the Oni Tormentor throughout MKDA-MK Armageddon,I would like Shinnok to buff him up with magic or some shit,so he would be MK's version of Bane (maybe not as smart,but his background in Deadly Alliance stated that he was a warlord,so it would be interesting to maybe make Shinnok restore that part of him a bit to give him SOME sanity,since he needs his mask to stop savagely killing everyone around him as hinted before).

And I would LOVE Sareena to be in this game. As you guys remember Shinnok imprisoned and tortured her after MK Myhologies (and we know those events happened in this timeline as well,Raiden hinted at them to Cyrax in MK9 when Bi-Han died),so it would totally make sense to make Drahmin her tormentor all these years. She would be perfect character to fuck up the plans for bad guys from inside,like to free Kuai Liang from Quan Chi's control since she had a brief history with his brother (maybe a little help from Scorpion since if spectre found out the truth about his clan and family and would want to come back at Quan Chi but since he is not that powerful to take powered up Quan Chi he would need Subbie's help even though he hates to admit it? See what I did there lol?)

So anyways,Sareena could be the one to take sub-boss Drahmin in this game's Story Mode and solidify her place in MK lore once and for all. She has motivation to fuck over both Quan Chi and Shinnok and become this complex hero that is tied to one of the mascots (Sub-Zero) and has her demon side to deal with (kinda like female Wolverine,who struggles with his berserk rage often).

Basically,Quan Chi is Shinnok's archsorcerer and potential subboss, Drahmin is his main muscle and bodyguard,also a subboss, and Brotherhood of Shadows members are his spies and best warriors against Elder Gods and Forces of Light.

If not some monster for subboss,then I would definitely would make tagteam sub-boss from the dead heroes,kinda like Noob-Smoke in Deception. It would be kinda symbolic to show how outnumbered and desperate heroes are that they would need to face their former friends. And there should be multiple sub-boss tag teams like that,for example,undead Kitana/Sindel or Jade/Kitana against Edenian character in the arcade ladder,Johnny or Sonya should probably encounter Jax/Stryker,Kano (if he is in) should encounter Kabal/Jax, Raiden should encounter Kung Lao/Nightwolf? or even Liu Kang/Kung Lao (if Liu's dead,but I am feeling that NRS has other plans for him rather than being Quan Chi's puppet judging from MK9 endings),etc. You get the idea.