If they did that I think a superbike F2 would become the new bike to beat, displacing the SV, which might not make Suzuki happy. I had one of the first F2's to make it Stateside, a 1991 model, so maybe you'd have to go 90.... :o
How about limiting 90 something or older to Supersport prep? But then enforcement becomes difficult, not that it isn't for other classes as well.