Something ive wondered about a lot is how when the resistence groups created the provisional government they decided who got what rank, since a lot probaly nominated themsleves for high office.
My guess would be that whoever had the influence to declare themselves generals would then have decided how to organize the former resistance members under them, and it would trickle down until everyone had been given a rank by the people above them.
To some extent, I'm sure they just made it up as they went along. For instance, once they decided to assign Kira to DS9, she had to be a major to fit in the right place between Sisko and the rest of the crew's ranks. Since they were making everything up from scratch, it's possible she was given a rank over better or more experienced people, just because that's the rank she needed for the job that would get her out of the way.
Although, she had been fighting for something like 14 years. It seems like it would be hard to be at war that long without being killed, so she was probably one of the more experienced members of the resistance anyway.