It doesn't matter if you find it entertaining. It should be about growing the sport. The attitude of big budget being more important than big balls is no good for any nitche sport. The guys watching motor cross are guys who want to do it, and anyone who can come up with 5k for a bike can go to the track.
I Remember watching a video of Malone when I was 16, saw the price tag of his ski and thought there was no way I could afford such a thing. In reality, it takes $2000. (For the kind of tricks he was doing at that time).
So let the low budget people have something to get excited about. Yu don't even need to have a set event for it. Exhibition 4 riders between races or something so it takes all day to complete the competition and no one gets bored.
Same thing goes for lower and vintage class races, which I've read people are suggesting putting them out of world finals.
I myself was excited to hear that pro-hydro X was going to do a vintage style freeride. I was practicing for it up until I got hurt. (Stick hull full limited driveline Superjet).
As for specs, I think it should be pretty limited, but not like racing that is particular about certain mods (like my lightened flywheel taking me or of limited spec). Build the class around the rider, not the rider around the class. It would be a recreational class, and blocking certain people over trivial little things that provide insignificant advantages defeats the purpose.