I actually came here to write just that. It's a good thing there are more people who like this idea, it means it may happen!
A natural evolution of this concept is to add a "b-class", a go-kart equivalent series, that is, tricycles.
And perhaps also an upper-class with more power, (tandem-bikes). The problem I see with this though is that we might be needed bigger circuits for it to be meaningful, though.
