I can understand that.
But here, you’re basically using categories a way Discourse isn’t made for if I understand Falco’s message.
I don’t know much about discourse development, I’m probably stating the obvious, but your category hierarchy seems, however, perfect for using tags and I guess it would completely resolve your issue (unless you have a particular issue with tags?).
Here, you could have this kind of hierarchy (category → tags):
Chevrolet
- Camaro
- #Camaro-II
- #Camaro-III
- #Camaro-IV
- etc
And so on for Cavalier, Corvette…
