This is not important at all and unlikely to be supported, but just
out of curiosity:
Is it possible to set matplotlib such that, when using the 'o-' marker
connected by lines) and partially transparent markers, the lines are not shown
within the transparent marker? That is, the lines would stop at the boundary
of the marker and pick up again at the other side. This would produce a better
aesthetic effect, I think, than the lines being seen coursing through the marker
when the markers are transparent.