During the Missile Base mission, Selphie leads the party into the base, however, why do the Galbadian soldiers in the base not question the fact that there is a woman in the base. Throughout the rest of the game there is no mention of females in the army, and not only is she far smaller in build than the male soldiers, but will also speak with a female voice (and speaks to guards on several occasions). Is there any canonical explanation for this?
I remember multiple occasions when the soldiers inside question her appearance though i can't remember if they referred to her as a guy or girl however we don't actually hear Selphie talk so for all we know she put on a deep voice (which i can totally imagine her doing).
however consider how Selphie's team got in, they use Galbadian Uniforms and a Galbadian Jeep, plus i'm pretty sure they had an access card to get in which was inside the jeep, Galbadian soldiers seems to be the arrogant type who would think that no one could get all of these things together, let alone a bunch of kids (if you chose Rinoa and Zell).
Now ever after getting in why didn't any Galbadian Soldier suspect her? they had no reason to, there was ways to sabotage the launch without being detected until the very end (i think there was also a way to never get detected). also Galbadia is totalitarian, so long as a soldier was loyal to the state i don't think anyone would question women joining.
Ofcause in a design point of view, remember that if you use an entire team of women their disguised models are practically identical to normal Galbadian Soldiers except for height, it's probably assumed that there are women Galbadian Soldiers but it would have taken a bit of time to add in models for them and have them randomized with the male models or create separate monster entities for female soldiers