I think VAs have a wide spread of power levels like the Warlords though not as extreme as Mihawk and Buggy. From fodders like Maynard to Admiral candidates and Garp.
I don't know if you have read Kingdom but the Generals and their subordinates sort of resemble this where there are strategists who have higher or same ranks as other generals and ranks but are individually weaker than people on the same or rank or even below them.
Basically until VAs your individual power level does not matter as significantly as it does for Admirals. If you have other skills like intelligence, charisma etc. which shows that you can take command of units then you can get to the VA position. However, for the Admiral rank you need to be a total power house.
At the end though it is just me trying to make sense of the big gap in power level in the VA ranks. Maybe some Admiral bros can shed more light on this.
@Elder Lee Hung @MarineHQ @SakazOuki