I don't believe there's a market for the idea you suggest. I mean look at the other franchises mentioned in the above, the pull and attraction far outweighs our show. Surely it's not a viable venture - as much as we'd like to see it.
As mentioned on another post just now, the Knightmare series would seem too obscure to the casual or impartial viewer. They haven't (as yet) brought out any DVD releases as a case in point, which is a great pity, but from a business perspective you can kind of understand the reasoning.