I think if it were mine, I would experiment with twisting the distributor to find the limits of initial when it starts to hit against the starter and then give it all it would take by shortening the slots.

Using either mechanical or vacuum advance to bring up the idle timing would very likely end up having a guy chasing his tail as you pointed out. Just putting it into gear or easing the clutch out would change the RPM/vacuum and thereby the idle speed/quality.