Captain Edition: what i can add.

[R4V3-0N]

ah, now I catch your meaning, but if it's pirate themed then it will still have to be random races. but can consist mainly of the home sector it's in. Mantis are known to have Engi slaves, and the Federation is the faction that consists of (so far confirmed)
Engi, And Federation. Zoltans to if you have done the Zoltan peace quest when they technically rejoin the federation.

Rock may also be a possible federation race but unknown. just saying.