My BOs, male or female, don't have an option to display rank while wearing TOS uniforms.
If you can't get you BO to wear the uniform, try a different BO. You might also try change instances of the area you are in or beaming back to your ship then back to whatever station. I find the costume interface to be quite buggy.
And there's the graphical bug where you can see their underwear during transport.
The skirt isn't synchronized during transport...Beaming up, it beams up first...then the rest of the model follows....
Hah yeah, I'd forgotten about that little quirk. Skirts also pose a problem when a female character sits in her Captain's chair in a very unlady-like manner exposing herself to her BOs and the viewscreen. They definitely need to implement the good ol' leg cross.