If you further divide your regional class by tire, does it not reduce your competition in each class? Our regional division, Great Lakes Division, used to have an open tire rule, in our divisional championship. When the new rules came down where the divisional series was a path to the Runoffs and competitors had to use the national tire, at first i was concerned.
However, competition is closer with everyone using the same tire. At our tracks, the Hoosier is a faster better tire, IMO, and the contingency and track side support from Hoosier is fantastic. The contingency is winner two tires 2nd one tire, per race and 4 tires to divisional champ.
Unless you run lots of NASA i see no advantage to the RR. 