This may be a small thing (and could even be added to 2.0 with a patch 😉😉) but in custom championships I think you should be able to choose specific cars in a class, not just the whole thing. The Historic championships have this already. For instance, in the first championships, there's an H3 RWD series featuring the 240Z and the Stratos. Then in the 80's ones, there's a series with the rest of that class' cars.
Something like this in custom championships would be really nice (for me, at least). Makes it easier to create a more authentic series.
EDIT: Another I thing I just thought o