I myself am not against this idea. The biggest objection that I can see is that doing so actually uses values outside the table (ie, the label column). I don't have a problem with the concept of perfect gunnery accuracy. In fact, I think it would help to legitimise the assigned value. For example, why is the WB value of the Lunar 6? What does the 6 represent? Answer: the maximum potential impacts. Without the chance for the Lunar to roll 6 dice (and the Dom to roll 12 and the Tyrant to roll 10 and Carnage/Emp 16, etc) then the value is a pure abstraction. Pure abstraction is fine, but we have an abstraction which is so close to the actual numerical value that it becomes confusing.
For example, if instead of having firepower 1-20, what if it was firepower A-T? So the Lunar would have firepower F, the Dominator would be firepower L, etc. Then a further left column shift would take the Dominator from 11 dice to "L" dice, which is meaningless. Of course, letters can't be added or divided meaning that combining and splitting firepower would be impossible without simply assigning a numerical value to those letters. Similarly any other abstraction would be able to be so categorised back into a simple numerical expression (category 1 firepower, category 2, etc).
However, if the values returned by each category were not fractions of 1 then it wouldn't be possible to simply use the firepower column. For example, if firepower 6 gave 12 dice in the defences column then a further left shift would actually reduce firepower by 50%!
In essence, this sort of thing would not normally fly, but in this case we have a chance to define firepower in real terms, rather than pure abstraction, and it's aligned to be doable.
TL;DR - Yes.
