I've been thinking more about the idea of new groups, especially since we can clearly see that many of the current groups don't necessarily entail cars that raced in the same group. The most obvious example being the Toyota GT-One TS020 being in the same group as modern Super GT GT500/DTM racers, but funny enough, I'm actually enjoying this sort of weirdness, even if it means notable changes in power/weight to make certain cars competitive. I'm also still unbothered by the sheer variety of Gr.1, especially since I think any issues could be addressed simply by having more events that limit players to certain selections of racecars within a certain group. Just as we've seen Gr.1 events that specifically focus on the Group C racers.
Ah, but I digress. I really do think there should be new groups for other race cars, of the especially historic variety. I maintain the notion that there's really just two groups that I think would be great: a "Gr.1V" and "Gr.3V," with the V standing for "Vintage." For the former group, you'd see racers like the Porsche 917, Ford Mark IV, Jaguar XJ-13, and the Ferrari 330 P4. Whereas in the latter, you'd see the Alfa Romeo TZ2, the Shelby Daytona Coupe, the Ferrari 250 GTO, etc.