it is entirely doable if you carefully maintain your rep... destroy pirate home bases as you find them, make peace ASAP, avoid wars against races who comprise a large portion of your empire, win wars rapidly, etc...
I have been dominating the galaxy without a problem that way. Just remember that your reputation is your most important value, never let it dip and you shouldn't have problems with revolts.. heck, you will have planets joining your empire as they rebel from other empires...
The point is tltamir, not everyone wants to play a nice guy. If there is one overriding path to victory, it's not much of a game worth playing... at least more than once or twice.
I am aware, I also don't want to play a nice guy, I was just saying its doable... and if you fight your wars quick while doing "good" things on the side (pretending) you can be plenty evil... just not get penalized for it.. fight one war at a time, maintain lots of free trade agreements, and crush your enemies fast while maintaining peace with other empires (aka, avoid multi fronted wars).
My point was that conquest victory is doable, it just requires knowing how to "game" reputation.
I have personally complained how reputation ruined me the first time around... i had a 300 planet empire, second biggest was 60, then a 30, then a dozen under 5 planets empires... Well, I didn't know how to maintain my rep so i got into war with ALL of them at once, then 60 planets split off into a rebel empire... my morale went into the crapped because for the first time i was fighting other humans, so planets all over my empire went into rebellion... yea, it was terrible. But know i know to "game" it so i can play right... and in my current game I am in a similar situation and just finished exterminating a few empires entirely AND I don't even have way of anicents! I managed to exterminate enemy empires as a democracy... and my reputation is the best in the galaxy.
I do not have a superman complex; for I am God, not Superman.