Good points Phee. There's no a reason a Rival can't become a Nemesis either, growing in power or influence as the PCs do. It makes for a very personalised experience for the players.
Haha, even a fully-modded ship isn't a match for that kind of enemy fleet! But hey, that's why these ships are fast and the PCs should have good pilots!
We even did some retcons when the Rigger PC joined our main EoE game - the players very much wanted to keep the Krayt Fang so we retconned it that the Rigger was the original inventor who built the ship from the chassis upwards. Of course, without her running it, it didn't have those enhancements. She wasn't, to put it mildly, happy to see what the poor players had done to her beloved creation...