Agreed, here are some things I would change, storywise.
MK1
Scorpion would not be an undead spectre, he would be Hanzo Hasashi.
He and Sub-Zero would be after the same taget, Shang Tsung.
Sub-Zero kills Scorpion to get to Shang Tsung but fail to kill Shang because Reptile gives him time to escape.
Quan Chi still kills Scorpions family.
MK2
Scorpion returns as the undead Spectre we know and love.
Smoke is a selectable character ready from the select screen but with different moves than Scorpion, like a smoke bomb for a warp and a grenade that pops the enemy into the air. (Just ideas.)
Smoke and Sub-Zero are after Shang AGAIN but they fail because Scorpion intercepts them and wounds Smoke. Sub-Zero defeats Scorpion again.
Liu Kang loses this time to Shang Tsung but Kung Lao defeats him.
Kitana and Jade turn on Shao Kahn foiling his plans of defeating Kung Lao, Mileena would be a secret character.
MK3
Due to the rules of the Elder Gods Shao Kahn cannot invade Earthrealm so he again hosts Mortal Kombat, this time with Shang Tsung, Quan Chi(Who is after the Amulet that Shao Kahn has), and Motaro.
Smoke and Sub-Zero are on the run from the Lin-Kuei for failing and they send Sektor, Cyrax, and several other lesser Lin Kuei after Sub-Zero and Smoke.
Lui Kang, Kung Lao, Kitana, Jade, Sonya, Johhny Cage,Jax, and Nightwolf all enter to stop Shao Kahn.
Kano, Kabal, Shang Tsung, Reptile, Ermac, Mileena, Baraka, and Sindel enter to stop the Earthrealm warriors.
Quan Chi is under false pretenses, he truely wants the amulet.
Sub-Zero and Smoke seek to redeem themselves by killing Shang Tsung and Shao Kahn.
Scorpion learns that it is because of Quan Chi that he died but it still after Sub-Zero as well as Quan Chi.
I'll do some more later....