nuTrek "Mirror, Mirror"!!!!
That should be fun. Although my brain is immediately trying to make sense of how it would work timeline-wise. Did they have a mirror-supernova, and Mirror!Nero or Mirror!Spock Prime go back branching the mirror universe in 2233?
The Supernova would have gone off and destroyed Romulus regardless, as that is because the star has run out of fuel to prevent its collapse. One story problem is that in the original Mirror Universe Spock is dead. So who can substitute for Spock? What's the name of that Vulcan lady who's half Romulan from the Wrath of Khan? Ah I got it Lieutenant Saavik, because of her half-Romulan heritage she'd have motivation to try and save Romulus from the Supernova explosion, and maybe incur Nero's wrath by doing so, only one problem, the Klingons destroyed Romulus before the Supernova did its work. The Romulans of the Mirror Universe are a planetless people, they joined the rebels in fighting the Klingons in the Mirror Universe books. The supernova would still explode, but the main villain Nero lacks motivation, but perhaps someone else can fill Nero's boots. How about Jadzia Dax, the Terrans exterminated her people under Spock, perhaps she could go back to the 23rd century and try to save her people from extinction, and maybe get some revenge against Spock while back there.
On second thought, maybe the Mirror Universe's version of George Kirk would go back to avenge his brother James, whom Spock killed, naw. Any other ideas?