Hopefully this means GT500 and GT300's on the same track!
Wouldn't be much different to the random lottery you get in a lot of events right now. For example, recent LMP1 cars with an Escudo along with 1960's Le Mans cars. The kind of lineup that was acceptable in GT2 but grating 14 years later.
Anyway as I have said before, ditch the categorisation of Beginner, Amateur, Professional because it's simply ridiculous. Then go with;
Manufacturer Races - GTR Trophy etc
National Races - German Championships, Italian Championships, restricted by HP or PP. I'm sure with a small amount of thought, PD could come up with a good idea.
GT League - Sunday Cup, Clubman Cup, have them limited by engine displacement or something. Include Karts in this category so it feels like some sort of natural progression.
Special Events - Like The Wind, and miscellaneous events like historic car cups like in GT2.
Endurance - Only if there is damage, and the AI is challenging, otherwise racing for over two hours is only about fighting crippling tedium. No thankyou.
Rallycross - I don't have any faith that the course maker will drastically improve, or that they will have the player racing ghost cars like in GT2. The rally courses will force the player to overtake slow AI at some point or other, and the stages will likely be very wide. So they should stick with rallycross, provided that the track is wide enough, and that the track isn't dusty.