User blog comment:Monkey d strawhat/How a VA moves up/@comment-5962458-20130210142942

I think the VAs are higher in rank depending on where they are stationed.The lowest are those in the four seas, then those in grand line, then the base commanders, and top of them all are those in marine HQ.

I agree with mangamaster that a seat needs to be empty in order for a VA to move to the upper rank or a special situation that requires extra forces.

As for the criteria i think they are quite objective.The strongest and the one who has strong beliefs gets the spot.