I suggested a similar thing to SirP right before the (then still AI-less) Alpha2 release. I told him to put up a large fleet at the homesystems of the AI player that you'd need to conquer to win the game
. You could expand this idea by creating a map where the AI players are all set and get automatic upgrades and ship type updates (ship class changes automatically when mean tech reaches minimum requirement for a better ship class of that type (type=destroyer, battleship, etc.) with the mean tech being developed by the human players in-game. You could potentially make everything depending on mean tech, number of fleets magically popping up at the given star systems which should be a fixed number that can only be reduced by human player invasions, intel points etc.. Then you could either set all those fleets uniformly distributed over your star systems or implement a simple random walk algorithm with the option to stay over an enemy system and either colonize if a colony ship was by chance in the fleet or bombard or invade if it's an enemy system. To make things diplomatically easier, just have the Klingons, Dominion and Cardassians have war instantly with every major empire they meet, Romulans remain always neutral and Federation tries once to get a friendship treaty and after 20-50 turns an affiliation with every empire they meet, the Ferengi just offer trade contact once in a while.
I don't if that's fun either to play or worth the time to code but it seems quick and dirty. On the other hand I can see people getting confused about this and not see that it's just a placeholder "AI" and thus condemning the game for a (intended) stupid AI
so it might backfire. On the plus side, you don't have to maintain the AI as long as the very basic classes and functions it uses aren't changed. Nevertheless, it's always better to code the AI properly right from the start. SirP and CBot did it in roughly 3 months. You can view the code on codeplex.