'One with the Spirit of Poontang'? Classic. I vote that somehow, some way, we get this in the game.
As for z's other ideas:
"Revenge" - well, it has the advantage of already, you know, existing as an option. However, I was never under the impression that the player was trying to avenge anything, but that's simple enough to change - just much with the starting text again, and voila!
"Diplomat" - I like the idea, but I'm not sure how it would execute. I see this victory (in either flavor, evil or good) as a combination of a lot of things: throwing money at the problem, using gangs, negotiating with rival gangs (which I'll note is not possible, yet or maybe ever), ensuring the removal of the old mayor (peacefully or... not), and of course, just general reputation gain.
"Whoremaster" - I think this gets in by default. Or, at least, the name - the victory condition itself may have to be tweaked. Just getting a lot of girls seems either too easy, or too difficult. Hmmm... I have to ponder on this one a bit, I think I have an idea on it. I'll get back to this at the end of the post.
"Mogul" - I dunno... having a money victory just seems like a cop-out. I think we can do better.
"Transcendence" - like I said above, we really need to get the 'Spirit of Poontang' in the game somehow. Not sure how this one would work... maybe, to do your ritual thing, you need to have one girl with a maxed PClove, one with a max PChate, and one with a max PCfear - plus a rare catacomb item? And a building?
"Other" - ah, yes, the mystical 'other'. Really, this one defies reason: it contains an infinate number of possibilities, but it is so rarely chosen. Spitballing ideas: something with the catacombs? I don't know how we could make that a proper victory condition. I might be neat to have a 'victory' condition based on how many gang members you lose.

Ditto for number of people killed in the dungeon.
Anyway, back to the "WM" victory: well, there is at least one significant issue that I see, and that is that the number of girls, and thus the difficulty, of this victory, varies from player to player. Not sure how to fix that, unless it's just to make the number requiredtotally arbitrary.
I wonder, would it be a good/possible idea to have your rivals actually have brothels, as in they own/employ girls (random and custom) of their own? You'd have to have a way to keep track of the rival brothels, perhaps give them incomes, they'd need a basic AI... hmm...
EDIT: Doc, exodia, play nice. I don't care who started it, I'm gonna end it. Don't make me sic zodiac on you.