Upon further inspection, it does seem like that race at Fuji featuring all the Nissan "Z" models only lets us rent the cars, which is interesting in is own right. It's over half a century's worth of different models, so I'm highly curious as to how PD plans to balance them - or at least try to.
Maybe we could see something similar, with other events modeled on the motifs seen in the various menus. I, for one, could go for a similar race featuring the Ford Mustang - which would include the older Shelby GT350 as well as the newer one - or perhaps the Corvette. Even an event based on the Viper, of which there are only three road-going models in GT7, could be real neat. Or perhaps even a broader event for any American sports car within a certain power and weight limit. BoP could be naturally disabled, but setting would only permit power, weight, and possibly one or two other settings, like downforce or gear ratio.
Honestly, it feels like the more I look at these regulations - at least for the Nations Cup - the more interested I am in participating.