I'm running out of superlatives, George! Just when we think we've seen it all from you you raise the bar again. This would work just as well if you had a scroll chuck in the headstock and a jacobs or collet chuck in the tailstock. Only caveat would be that the tailstock has to be very accurately aligned with the headstock, but that's true of normal mandrels too.
I'm a little envious of your adventures with the treadle lathe, in the spirit of actually DOING something as opposed to just pressing buttons that must be extremely satisfying!