I would take it a step further, and stop determining how many bands advance to state based on the number of bands that *qualify* for Area (which I think is what you are getting at).

Think about it...what contest advances bands to state? If you said "Area" you are only half-right.
It is Area *finals*, technically a separate contest, that determines who goes to state. How many bands are in an Area finals contest? At most 10. That means that at every Area, there should only be 2 bands advancing in 5A & 6A, and 3 in 4A and smaller.

The only time more than 2 or 3 bands should be advanced is in situations like we had a couple of weeks ago...when inclement weather forced the Prelims contest to stand as the Finals. In that situation, then you can use the "1 for 5" rule as there are more than ten bands performing.