I defintely see the lack of readily available accessories as a major downside to the Xpan/TX system. I have the TX-2 and the matching 45mm lens brand new (no hood unfortunately). I just "upgraded" my champagne-colored TX-1 90mm that had no hood or cap (though it did have the bubble case and included rear cap in the base of that bubble case) and got the matching TX-2 90mm that was complete with an included hood. It cost a pretty penny to upgrade, but I got sick of waiting for very rare accessories to pop up. Good thing is one hood works for both the 45 and 90mm so while I'd like two for completions sake, I'm fine with the one for now.
Though back to your point, depending on how they are manufactured, and price, I'd guess there may be a limited market for it. I'd like to see what you have on offer at some point regardless.