The issue with this is doing it in any sort of consistent way. What is the difference between a double IPA and a triple IPA? The only two options are either go with what is on the label, or use an arbitrary ABV. If you do the former then you put this 11.5% IPA into double IPA
but if you do the latter then you put something which explicitly calls itself a double IPA into a style called triple IPA. There are also lots of breweries who just call their 10%+ IPAs as imperial IPAs, so which do they go into? Then you have breweries who market even stronger IPAs as quadruple or even quintuple IPAs, where do they go?
There is a pretty easy solution, which is that double IPAs, triple IPAs, quadruple IPAs and imperial IPAs all fall under the bracket of imperial IPAs, which is half of the style name.