I remember when I was in the navy. It is not against the rules to have relationships. It is not a good idea to ever let them interfere with work though. Infact you used to be able to get accomodation together. Officers and enlisted ratings was never a good idea though. Sex on battleships was not really allowed but then neither was it disallowed. Just happened and everyone ignored it. It meant that a lot of people performed better cos they had some release.
As for story endings. I hate when there is too much left undone, makes me feel cheated somehow.
I remember in End Run that Jason--I think that is the main character, been a while--said that even though the military looked down upon fraternation; there were no rules or regulations against (or for) fraternation between officers, enlisted men and women, and even different branches of the military.
It is also mentioned in end run that Jason could have married Svetlana, if she wanted to, and a captain can marry two people, even in reality. Now I don't know if they were able to do so because they were in two seperate branches. Also a high up military personel, can't think of name or rank on this one, also sent Svetlana to Jason's room in which it is implied (at least to me) that they did have sex. Once again you have to take into consideration that they are in two different branches of the military.