Well, if we handwave the feasibility of the premise and get straight to the good stuff, the first thing to do is compare populations. I imagine the MU has a much larger population than the tribes of Spherus Magna (Tesara, Tajun, Vulcanus, and Iconox are really the only four still welcome in society, unless the Earth tribe is much bigger than we thought.)
I also think it’s safe to conclude that MU beings would be more likely to vote in an MU being than an SM being. Obviously that’s far from a ubiquitous trend, but across a whole universe I expect we’d see them favour… y’know, not a literal alien. That sounds mean, but if Earth crash-landed on an alien planet I guarantee you humanity would be voting in a human president no matter how nice the aliens are.
So that means we can rule out Raanu as a winner, though he’d definitely run. I don’t think any of Mata-Nui’s close friends would, nor Toa like Tahu who strongly believed in his cause, as MN made it very clear that he didn’t want a single authority ruling over the MU before he “left” and I think they’d want to honor that.
Dume… I mean, maybe? We don’t know much about him. Velika would obviously run because it would make his plans so much simpler if he already had a degree of power… although there’s a chance he’d prefer to take things by force, especially if there are other GB’s that he suspects might be watching.
On that note, you can safely rule out any other GB’s from even considering running, given their track record.
I think you’d definitely see some Skakdi trying to push a campaign, and a load of Vortixx given their cultural tendencies. Roodaka might run, but depending on the proposed political structure, I see her as being more likely to try and side with the leading candidate than trying to be that candidate.
Pridak, because duh, especially now that his mutations are reversed. Takadox might go for it too, although I suspect he’d be cautious. Maybe Kalmah too, actually. It was a long time ago these guys were around and they weren’t universally hated (though they weren’t liked, either) - I suspect they’d give it their best shot. Not sure if any would even stand a chance except maybe Pridak.
I don’t think many of the other big players would run for it. Most powerful authority figures in the MU are secretive and not necessarily politically inclined - you won’t be seeing Artakha or OoMN members running. Miserix wouldn’t give a Stone Rat about the whole thing, you can be certain. TSO won’t bother, he’s busy plotting with his new viruses, and so by extension you can basically rule out any Dark Hunter from running without being assassinated mysteriously before election day.
Actually, of all the characters we know, I suspect that Jaller would be the best bet for a winner. He’d certainly run. He has a strong enough sense of duty to want to have his voice in the position, he’s used to positions of authority, and I can see him deciding that if someone is going to end up president of SM, he might as well give it a shot. Hahli would no doubt encourage him to do it… in fact, all the Mahri would, if they’re free from the GSB’s control at this point.
If Lewa’s back from Bota Magna, he’d run just for the lols. Actually, count Kabrua in too, unless Velika is running.
And I think you’d see some Matoran - especially from islands without Turaga, like Voya and Mahri Nui. Defliak would almost certainly give it a shot, as might Dalu, actually.
As for who would win? No idea. We can’t even predict real elections in localised states very well, we’re certainly not going to guess the winner accurately from an fictional two-universe merger. Odds are it would be someone we’ve never met before, with strong political skill and campaign talent.
Finally, you’re right - if Vezon is present, he’ll try to run and pull a Hoseryx, or even just flat-out expect everyone to love him. I see him getting caught out immediately, identified, and jailed/exiled.
So… did I overanalyse much? 