There isn't a way to make a hard-tail kit that would be universal between XS, KZ, CB etc.
I have a ton of pics of oldskewljay's scoot. It doesn't get much better than that.
Scott, if you decide to go ahead with this I'm interested in one. I have no doubt that you could sell these. The Lorena Bobber frame is unique and just about flawless. There will be plenty of guys happy to jump at something different.