z-index and clipping

Hello SVG WG,

May I suggest for future SVG specifications, that the z-index of polygons,
lines, etc., could be subdivided into parts using coordinates or percentages
(for lines)? I.e., a particular polygon could be split into 4 or 5 polygons
of varying dimensions, each with a varying arbitrary z-index. Each part
would be rendered as a separate polygon inheriting the properties of the
original. On top of that, maybe it would be possible to alter the properties
(fill, stroke, etc.) of these subset polygons using the dom?

Failing all that, is there anything new planned for z-index?

Thanks,
Alec