I put this in the 1.03 wishlist, but it's a little too ambitious for a small patch. Reposted here for general discussion

Slavers/Reavers/Blood raiders

Have a mobile pirate-like NPC race! Have them only "settle" in asteroid belts or storms, places players can't colonize. Have them move to other systems on occasion. They could be a lesser race, whatever.

They could be based out of a couple of large factory/motherships and focus on disabling ships and going for planets, leeching populations, etc. Maybe they could capture cap ships and drain off some exp (taking crew members).

This is what I envisioned the Advent as being, actually, with the whole exile/deviant approach.