Not a full response, but why shouldn't you be allowed to choose hybrids on a road track? After all, that's why they're called hybrids, surely?
It allows one to choose the balance of the car, putting hybrids on the back of an XFG makes it less understeery so it's not an exploit... it's just tuning?
But I don't understand what you mean by "exploit setups"... it's just taking advantage of a faster setting, which is open to be chosen by EVERYONE.