And a Count. :rofl:
It's really hard to say if these people are hanging out on Efate or leaving it in the competent hands of local officials and the Navy.
I'm thinking the old game Kingmaker might provide a potential model.
youtube vid for any who don't know it
https://www.youtube.com/watch?v=URKlXEaVack#t=37
In that game you have nobles, nobles with permanent titles, titles that can be assigned to nobles who don't have one and offices. Nobles without titles can be assigned titles and only noble with titles can be appointed to offices.
Example
Cochrane joins the navy and rises to Captain, automatically knighted (not hereditary though) rises to Admiral, automatically ennobled entailing made hereditary knight and given a fiefdom like a hereditary pension (a knight's fiefdom could be something like a percentage of the local star port's revenue). This brings him and his descendants into the noble class.
Once a noble Cochrane can be given a title and an office that requires that level of nobility e.g. Baron and Governor of Barbados, or Baron and Baron-Commander of the Regina x-boat service, or Count and Count-Commander of the Deneb sector Scout service.
Cochrane's offspring start off as knights but won't get titles unless they prove themselves. Say the first and second generations also enlist in the navy but don't make it to Captain. The third generation does and gets a knight level office e.g. Knight-Commander of a space station somewhere. The fourth generation makes it to admiral again and the family get a second fiefdom and the 4th gen dude serves a term as Knight-Commander of Gash, then gets a Baron title and office of Baron-Commander of a colonization project for a term, a count title and office of Count-Ambassador to Fornice for a term and finally a duke title and office as Duke of a sub-sector.
A bit like the Roman Cursus honorum:
http://en.wikipedia.org/wiki/Cursus_honorum
Initially the specific titles and offices might have been kept separate from membership of the noble class but over time elements of heredity start creeping into the system so it becomes more jumbled like Kingmaker with occasional rebellion-causing attempts by the Emperor to reverse it.