How about something like a 4-track informal rotation of short oval races, do-able in one race session?
Example: Michigan, Orchard Lake, Milwaukee, Twin Rings Motegi... each for approximately 20 (?) laps.
That could require minimal pre-race practice, unlike the road courses, and it could be just one race weekend... But just throwing out ideas.
I tried CART Factor at (TPSCC) Louden with the short oval setup option, and then Michigan with the speedway setup option... crazy-fast stuff.
[FYI, the TPSCC tracks are avialable here: http://www.thepits.us/?page_id=6
I ended up looking for more of the ovals, either from the 1998 CART season, or mentioned in the mod's readme,
There's even a Twin Rings Motegi oval available (a WIP at rFCentral) -- An egg-shaped course that's not a standard oval.
With or without an online series or session, the CART Factor mod's definitely worth a try.