Well first of all, your definition of canon is rather loose it seems. Unless it's been confirmed by Nasu offhand somehwere, the Visual Novel does not actually point it out. It's mostly portrayed as a hunter-prey kind of deal with obvious fanservice/joke connotations.
Secondly, Ayako very clearly opposes the idea intensely and is afraid of Rider. Crack ships are usually ships that cannot, should not or make no sense to happen.