I was playing a 4-player game last night, I think the map was Wrathful (fun map by the way!).
I was playing Advent and I happend to exteriminate one of the computer players close to me. So I deciced to go after the Pirates next as I was allied with another player.
I jumped into the Pirate Base Planet and held my ground away from the planet's defenses (which happen to have a longer range than Torpedo Cruisers by the way) and managed to take out the defenders.
Next I built a Starbase and researched 2 Meteor Control updates and subsequently destroyed the Pirate planet. I moved my Mothership in and colonized the planet.
Here's the exploit: At this stage, all the Pirate planet defenses were still in place and now I had the best defended planet in the galaxy (each Beam Defense Platform had 4900 Hit Points)!
Advent seems to have a distinct advantage by far over the other races here as I can't think of another race that has a similar capability at least at that stage of the game (6 military labs needed to get Meteor Control).
I can only imagine the benefits being more in a map where there are multiple Pirate bases or the location is much more strategic. The only drawback I see with maps with multiple Pirate bases is that the Pirates could come in and easily attack the Pirate base you captured (if they select it as the planet to attack). I'm also not sure if the Pirate defenses would continue to improve in a multi-Pirate base game after you colonize the planet, but if they did this would make the exploit even more valuable.
This seems to be a consequence of the beefed up Pirates, and so not sure if a solution is warranted (or how to implement one at this stage), but Advent does have a distinct advantage here.
What do you all think?