Some nice progress in the latest wip: V5 geometry accepted now, lower polycounts by default. Seems that symmetry evaluation still needs some tweaking, but perhaps this falls into the realm of Rhino's shell function too, as the command failed creating a symmetrical offset of the input polysurface. Maybe something for @chuck to look into?
I think a globally available object property "symmetry" (which all commands had to respect) would help Rhino in just countless areas – it's the only 3D app I use, where this feature is practically non-existent. Attached is another test file, some play with axis and radial symmetry and also the effects of seams being moved around, while not actually changing the shape of the underlying Nurbs model. In an ideal world the mesher would understand, that it can savely disregard the orientation of seams of some ring shaped surfaces and instead prioritize a symmetrical and orderly outcome :o)