I think that taking a page from SCCA might be a better idea. they have regions with their own events, plus a few major events that bring in racers from all over and then finish with a national championship at the end of the year.
Make it a full week event much like the Runoffs. have 2-3 carpet events and 2-3 asphalt events that can offer double points throughout the year or some sort of incentive and then have the top 2-5 in each region points get an invite to the end of year nationals. You could have these classes (using the ROAR class structure):
Expert 12th
Expert World GT (10.5)
Expert Touring
Sportsman 12th
Sportsman World GT (13.5)
Sportsman Touring
Open 12th
Open Touring
F1
RCGT
Vintage Trans-Am
This is all just stuff I have in my head right now but at least this is being thought about again