Funny that you mention Cinder in the OP. I have been wanting to see the KI cast merged with MK for a while and here's how I see it:
Fulgore - Ultratech rivals the Lin Kuei with their own cyborg. Fulgore's real purpose is to find and defeat Goro, and bring him back to Ultratech...to be cybernetically enhanced and meshed with Fulgore to create the ultimate fighting machine... FULGORO!
Glacius - The race that originally taught the earliest members of the Lin Kuei how to master the cold. Finally free from Ultratech, Glacius realizes that what his race taught the Lin Kuei is being used for assassination...his goal is to stop Sub-Zero at all costs.
Cinder - Cinder is attacked and subdued by Shang Tsung. Believing him to be a similar being to Blaze, he is forced to fight in the Mortal Kombat tournament in case Goro should fail.
Jago - After much research, he learns that both Gargos and Eyedol were enslaved by a mysterious sorcerer named Shang Tsung. Burning with desire to exact his revenge against the "Tiger Spirit", Jago enters the Mortal Kombat tournament seeking to destroy both demons' true master.
Orchid - Now working with the Outworld Investigaton Agency to uncover the truth behind why Shang Tsung has an interest in Gargos and Eyedol.
Riptor - After the Killer Instinct tournament, Riptor learns the truth about his origins. He is a clone from DNA that Ultratech could not identify... Riptor's only clue to who he really is comes in a direct message from Raiden himself... "Find Reptile and defeat him..."
Sabrewulf - As Sabrewulf begins his descent into madness, he has visions of a Shaman who can channel the spirit of the wolf. Knowing he does not have much time, Sabrewulf seeks out this Shaman, hoping that he can help him at least retain his sanity before he falls entirely into feral madness.
TJ Combo - Recruited by Kano after the Killer Instinct tournament, Combo has the only cybernetic arm implants strong enough to compete with Jax. Defeat Jax, and TJ Combo is promised all the wealth he lost before he was thrown out of Professional Boxing.
Spinal - Hunted by Shang Tsung, Spinal's soul is magically bound to his bones. Shang Tsung will stop at nothing to steal it, and Spinal must compete in Mortal Kombat to fight for his very soul.
Eyedol and Gargos - Resurrected by Shang Tsung without the knowledge of Shao Kahn or Goro. Tsung intends to use these mortal enemies to help him enslave all of Outworld and the Earthrealm...including Goro and Shao Kahn.