Reverse Empire Building

Cooperative games have "you all lose" as their natural state and it takes good play and multiple efforts to win one; they're very hot and very few people truly complain about them. Also, if you have some way of keeping score, there will be one player who lost less than the others and will be the winner.

As said above, don't worry overmuch about other games --- the only time it is ever an issue is if you knew about a (developed) game idea or mechanic and used it. Accidentally copying someone else without even knowing it is fine, but extremely unlikely. Look at a couple of game contests here... we all start with a specific set of requirements for the game, but almost every game produced in the contest is distinctly different from any of the other entries.

Perhaps each player plays a certain member of leadership. (Have more leader choices than players, so some are left out, leaving your populace exposed to one threat or another.) Each character has a responsibility, and how much they end with compared to others determines the "better winner" if they all win. So, perhaps one player is trying to control populace, but the general, who is trying to win wars, needs men and women to fight. So, he has to take people from the first guy. The economist has money and needs money, but so does everyone else, so he has to loan out money, just as the first guy has to loan out (or give out) people.

I'm not one of those experts on every game that has been or is coming up for release, but it sounds like a new concept to me. Besides, even if someone else has done a take on it, there are a lot of games out there that share themes and even some mechanics but have small differences which add up to radically different experiences for players.

I could see where you're concerned about it being too challenging, or perhaps that it could be a downer to face the annihilation of your civilization (rather than being the one to create and shape it), but I think you could set the tone of the game so that it's really fun. I think it sounds ripe for the injection of a little dark humor, but there are other ways you could go about it, such as having a really creative or compelling back story that presents the challenges facing this civilization and maybe some of the factors in its downfall. A rich setting like that could really spark players' imaginations and get them invested in preserving their civilization.

It'll be interesting to see the rules and how you implement all this stuff. Seems like fertile ground in mostly uncharted territory, so it's bound to be fun.