i haven't played 1.2 yet, and don't play at the hardest levels or anything, but i do prefer playing on the largest maps... gotta have that epic feel, me.
and i agree that the "once you start winning, you keep winning" syndrome is present in GC2, as it is in all 4x games.
but i don't agree that it is present moreso than in, say, Moo2 or Moo3, or the Civ series, or SMAC, and so on. i'm not sure how i'd measure that, anyway!
in Moo3 there's an emergent phenomenon the community calls the "Lone Superpower Effect", where once you're in the lead, the AI players start to turn against you. interestingly, the modders/patchers who've taken the game apart and put it back together again assure us that in fact there is no such code in the game to make it do that!
the best we can figure out, the AI players start to get upset when there are no planets left to settle, and the ones they do own start to fill up... and who do they get upset with? their neighbors. and who tends to be everybody's neighbor? the Lone Superpower!
in any case, having a Lone Superpower Effect seems to be what people are asking for above.
but what was the result in a game that had it? you guessed it: people complained about it, and wanted it taken out.
why? because they spent the early game building alliances and making friends, and in the endgame their friends would start turning on them, and backstabbing them!
for players that prefer a diplomatic game, such an Effect can be extremely frustrating!
in it's extreme form it can make the Diplomatic/Allied victory condition degenerate back into the Military/Sole Survivor victory condition, since each time you take out a traitor, it makes you stronger, which promotes further defection, until you're the only member of your once Grand Alliance left! (thankfully, in Moo3, we've figure out how to avoid the worst effects of the Effect)
so while i think in the later game that your enemies should indeed band together and come after you if you're winning, it should be implemented with care...
your Allies shouldn't turn from you, for example! why would they leave the winning side?
and empires with good relations who can see the writing on the wall, wouldn't they want to sign up as Allies, so that they can be on the winning side?
i don't know if GC2 AIs do "Enemy of My Enemy" thinking like they do in Moo3, but one thing Moo3 got wrong (imo) was to have the effect decrease over time, instead of increase.
in the endgame, empires should be looking for Friends to help them fight, and Friends-of-Friends and Enemies-of-Enemies are who they should naturally gravitate towards.
also, they should increasingly turn their destructive attention on Enemies-of-Friends, and Friends-of-Enemies... for example, they could look at the worst Enemy of their coalition, see who the weakest Friend of the that Enemy is, and all attack the weakling... forcing the stronger human player to help defend the weaker AI player.
if the Superpower didn't come to the defense, their Grand Alliance would be made weaker, while the Enemy Coalition would be made stronger, right? or, if the Superpower tried to defend all it's weaker friends, it might be stretched too thin, and become vulnerable to a coordinated strike?
if done right, enhanced
Enemy of My Enemy type thinking in the mid/late game might have the effect people are looking for, without breaking the Diplomatic victory the way a
Lone Superpower Effect would?
and yeah, i'd like to see more likelihood of
Lost Elections and things like
Civil War (perhaps as a result of a lost Election?) or
Revolting Provences breaking up a Superpower... that would be super-shweet.