Why not have them work together?

Why would Scorpion care if his old, but completely false nemesis is back?

Bi Han wasn't the one who slaughtered Scorpion's clan, Quan Chi did. If anything Noob should learn the truth and want to kill Quan Chi for having Scorpion murder him during the tournament. All because Quan Chi made him, just to have Bi Han's soul. So yeah, I don't think having them fight, or your first reason to be logical.

Sub-Zero may not have killed the clan but he did murder Scorpion and I'm sure Sub would want some payback against Scorpion. Not that I remember but I don't think the two of them have ever even "met" after Noob's resurrection as a wraith.

It makes much more sense for them to fight together against Quan Chi and Shinnok. That would be one bad-ass Deadly Alliance.

Noob Saibot is basically Bi-Han's true self,the side of him that made him famous as a warrior,that cold blooded merciless son of a bitch. He basically rejects his old life when he tells it straight up to Kuai Liang in MK9 that Quan Chi restored and perfected him,which means he is GRATEFUL for the way he is. Why you guys think that Noob Saibot will go against Quan Chi,the guy who made him more powerful than ever before and who is by the way his master and can strip him off his power real quick? And plus with Scorpion,the guy who murdered him. He might even be thankful to Scorpion,again,for making him stronger. So either way,Noob Saibot wont care much about Scorpion or killing Quan Chi just by judging his personality in MK9.

If there is something human left,it should be in Kuai Liang's soul,not Bi-Han's.

Nah IMO. While I didn't like MKs story mode, one of the only well written bits was the Scorpion/ Bi han chapter. He got his revenge, it was dramatic, it was glorious... It's over now. As far as scorpion is concerned in the rebooted cannon, hes fulfilled his destiny. Now he serves Quan Chi until he finds out it was him that killed his clan.