Actually, I just found a Marine squadron for you - Hell's Archers Squadron is VMF544, assigned to the TCS Ark Royal (per the WC:CCG shirt)!
I don't remember any other references to squadron designations, where are those from?
They're all over the place. Including:
* Victory Streak has a list of squadrons which have won awards at a recent competition.
* The Heart of the Tiger novelization talks abotu the Victory's wing (36th FW).
* The Confed Handbook has information on the Tiger's Claw's wing (88th FW) and about the various squadrons and the Space Force assigned to Pegasus.
* False Colors talks about FRLN squadron and wing designations throughout and also uses them in various chapter headers.
* Voices of War references "Squadron 23" in its simulator competition advertisement.
Now that you mention the movie, yeah, that is something that bugs me in the movie and then I promptly forget about it. Maniac definitely calls Rosie "marine" during the crash scene. The whole Marine angle would have made the Comcon boarding scene make more sense.
The problem with the Comcon sequence is that almost everything is cut out. Blair *isn't* supposed to be one of the Marines... in the film-as-shot he's Paladin's turret gunner and he disobeys orders and boards the ship when Merlin detects the traitor's signal.
Angel *is* one of the Marines (though I'm not sure she's visible in the final cut). Per the novel she's leading the boarding party because she once trained on a captured Dorkir. The rest of the marines (Sgt. Cogan and his subordinates) are unique characters and actors.
Maniac's 'Marine' line is a strange leftover from an earlier draft... like the 'everyone you know will be dead and buried' conversation between he and Rosie in their love scene (which was leftover from an earlier script's premise that jumping through space was a Forever War-style one way leap forward in time).