[sgqwonkian]

It would be tricky to have this swap from session to session, seeing as how there's the ambassador quests for it to conflict with. I suspect you don't want to try to trigger it at the start of the game, because their default settings may load after your quest. If multiple alliance-changing quests trigger, it's possible the game might only register the first or last one. I know sometimes it has trouble with that sort of thing.

Instead, you might try setting it up as a event triggered on a planet. (Those usually work more reliably.) Sort of a pandora's box thing, where some event happens that changes the alliances throughout the sector. Make several versions of the quest, all the with the same KEYS so only one can trigger per game.