Ah rushing. So annoying. I wish Sins had the feature that Rise of Nations had. You could set a timer on how long until aggression could commence. Like, say, just put a 15 minute "all peaceful" mandate on the game.
Anywho, the best rushing tactic is Illums with a mothership just because of the sheer power. Starbase rushing can stop it at one planet, but unless that planet is the homeworld, the illums can just go somewhere else.
My personal favorite has gotta be using a Revalation with a mix of light frigs and scouts for support. I'm dead serious. The Revalation makes the enemy ships hold still ( just takes the enemy cap out of the fight, early on that's a pretty big blow ). The Scouts can fight off any lrf's that come out (cause that's what seekers do!). The light frigs take out the frig factory. Bam. It tends to work purely because no one expects it. It goes to hell if the guy has backup from an ally (of course, most tactics go to hell when that happens anyway) or if there are too many Assailants.
It's kinda interesting how the Caps have worked out for rushing. Wish there was a bit more flair in some of the caps. We don't see 'em enough.
Actually, I almost always scrap the capital ship factory, but I almost always construct another one later. It's rare I go with just 1 cap. I realize getting 300 cred, 75 metal, 50 crystal, or whatever it is (it's around there) isn't much, but considering that money can pay for upgrading the population on the asteroid and then frees a spot on the homeworld for either a lab, or if I'm advent, a culture hub (which i always get if I'm advent, and to a lesser extent Vasari too).
It's enough of a payoff early on that I really think the building needs to be scrapped. When you only make 11.4 cred per second, 1.4 metal, and .9 crystal, that's a pretty big early boost to the economy.