The only GM invasion I didn't care much for was the 4th, which seemed a little inconsistent, overpowered, and then just went a little nuts with the "Light" being introduced just to end it. I still think the only reason people did complain quite as much as they did, though, was mortality.
Anyways, something I loved about the fifth invasion, story aside, was a simple mechanic. I n the previous invasions you had immigration to BT cut off. I enjoyed the fact that it stayed open this time, giving everyone a chance at the fun. Please keep that as a constant, even if you have to make new arrivals shipwreck near random ports- let them at least keep coming.