Would this Medici be brass brazed or silver brazed? Silver might allow the downtube to be heated enough to be pulled without necessarily compromising it through a third heat cycle. Possibly. Either way, it'd just save from a lot of die grinding to fit the replacement tube.

Is it worth it? Probably not from a pure economic standpoint (including repaint costs), but if the frame is sentimental and you're willing to cover it, it's definitely doable.

-Kurt