Tooling around with Ultimate X-Spanse. I don't think there's any kind of tie-in comic planned, but one popped, fully-formed, into my head, so I'm spitting it out.

Years ago Alpha Trion, while saving the lives of Orion Pax and Ariel, saved a small portion of each of their sparks. Sometime in the near future these portions of life-essence are combined into a new being, XSP92, who is for all intents and purposes, Optimus Prime and Elita-1's son. (Before you roll your eyes, yes this is a jokey riff on the X-Men alternate future child trope, no this is not a serious OC of Optimus and Elita's kid.) He is born into a terrible future, where the entire galaxy is ruled by an all-powerful madman. Cybertron is destroyed, and the few remaining Transformers are refugees, a small clutch of rebel holdouts. Their only hope is to send XSP92 back in time to the moment when this madman found the power source that elevated him to godhood but shattered his mind, and stop any of this from happening.

XSP92 travels back in time, to the planet where the galactic despot first rose to power: Earth. Upon arriving, XSP92 scans the first vehicle he sees, the X-Men's Blackbird. There are three lifeforms inside... Wolverine, Cyclops, and Psylocke. Ordinarily his scanner would have no trouble filtering them, but these lifeforms are mutants; his scanners malfunction and attempt to scan the jet and all three inhabitants at once. He mimics all their powers, and for a time, goes nuts. He takes the name Ultimate X-Spanse, and fights the X-Men, while speaking entirely in riffs on Claremont-era catch phrases. He's the best there is at what he does, bub. NO! His ruby quartz visor! If he opens his eyes even a fraction of an inch... you get the idea.

The fight ends when Optimus Prime appears; the sight of his father snaps X-Spanse out of his mental haze. Optimus is here tracking a Cybertronian crisis... the Underbase has resurfaced, headed for Earth once again. It shouldn't be a problem though... its course will cause it to collide with an asteroid in orbit around the planet, where they should be able to go investigate at their leisure. The X-Men panic though; the Underbase is due to collide with Asteroid M. They explain that this is home to their worst enemy, a man to whom Cybertronians will be uniquely vulnerable: Magneto. X-Spanse puts the pieces together, this is the moment his future's ruler was born. Optimus and the trio of X-Men agree to team up to avert this crisis. X-Spanse's experiences on Earth have clearly had some lasting impact on him, as he tells them they are willing to sacrifice themselves... can he do less? Better to fight and die, than live with the knowledge that he ran! Let's give the Underbase the worst case of indigestion it's ever had! "Who talks like that?" Wolverine mutters.

On Asteroid M, Magneto has indeed discovered the crashed Underbase. He has just begun to probe its secrets, and is staggered by the potential for power within. As he resolves to plumb the full depths of the Underbase, the heroes appear. The X-Men confront Magneto as Optimus Prime and X-Spanse work on the sending the Underbase on its way again. Optimus has a plan to use the Matrix to dampen the Underbase's power just long enough to dislodge it from the computers of Asteroid M and launch it back into space, but the Underbase lashes out and knocks Optimus out of commission. X-Spanse, however, uses his connection to Optimus's spark to manipulate the Matrix and complete the plan.

Magneto is furious, but knows when he's outmatched. He hurls everyone from Asteroid M; the X-Men ride inside X-Spanse while Optimus hangs on to his undercarriage to get back down to Earth. One thing puzzles Optimus though, how could X-Spanse have possibly used the Matrix? Who is he, anyway? Cyclops pats Optimus on the back of the calves or something and assures him it's probably complicated.

Optimus returns to Cybertron. He offers to take X-Spanse, but X-Spanse declines. With the future changed he can't really go home, and feels he has to figure out his place in this new world. And while that will be a burden he has to bear, at least the threat to his time is over -- finished! But at the end he sees the glint of the Underbase overhead, still hurtling through space... never really the end.