It's an idea that wouldn't really take much effort to implement but all stage fatalities will stay the same.

Some more suggestions

Motaro's subway fatality against humans/humanoids (including the cyborgs): Motaro moves his opponent near the ledge, and when the train passes, he kicks his opponent's head against it, smashing it violently. It could be followed by Motaro raising his front legs high in the air, and crushing his victim's ribs.

Freddy's stage fatality: For many stages with deadly environmental hazards, Freddy would cut open his victim's tendons and use them as strings, dragging the opponent to his/her death. When done in the subway, or the streets, instead of cutting the tendons, he'd have the train/car separate him from them when running over his victim.

Noob Saibot's pit 1 finisher against humans/humanoids (which once again include the cyborgs): He teleports behind his opponent and grabs him/her, but this time reappears beneath the pit near one of the pillars, and rubs the victim against the spikes all the way down, and right before landing, Noob releases his victim and vanishes. Alternately, he could just impale his victim on one of the spikes then teleport back on the pit. What the hell, he should be able to do both.

Ermac in the deadpool (could also be Kenshi's): Levitates his opponents, bringing them into a laying position, and rubs their back against the acid, lifts them up, positioning them on their belly, rubs them against the acid again, and finishes his opponents by putting them in a diving position and letting them go.

Ermac/Kenshi on the pit 1: levitate their opponents, position them between two pillars, and send them flying repeatedly against both pillars' spikes until they've taken them all the way down.

I believe in the potential of character-specific stage fatalities and deaths, so I will not let this thread die so easily.

Motaro's subway fatality for the Shokans: Motaro grabs his Shokan victim, and when the train arrives, he gets the Shokan's right arms in it's way, tearing them right off, repeats it with the left arms when the other train passes by, then he slams the Shokan head-first through the ceiling, leaving them stuck.

Kintaro's street fatality for Motaro (and any new Centaurs): Kintaro jumps away, lands near a tank, grabs it and gets back to Motaro by jumping high in the air and smashing the tank on top of him. Kintaro throws it away, and sees Motaro is still alive, but barely. Kintaro grabs him by his tail, smashes him on his head, and swings him around begore finally throwing him in the river.

Motaro's deadpool fatality on humanoids, including the Shokan: Motaro grabs his opponent with one hand, and smacks them in one of the chain hooks with the other. Motaro then proceeds to continually beat up his victim, punching and kicking him/her away, and fires an energy ball from the end of his tail at the chain, destroying it, resulting in the victim falling in the acid.