>> But in relation to one another the way I was thinking would be to do it by surface area of the 3D polygons.

So for instance the corner patch in a filleted box would get a smaller UV area than a larger sized piece.

Yes what's I have in mind in fact, distortion can be fixed with a uv unwarp package.

It's an old workaround used in Rhino to force tesselation where the mesher doesn't find the solution on it's own. So yes, I mean you can try splitting the object then rejoing to make "user-defined" polygonal boundaries...

Hi there

T-Splines can sometimes produce the kind of UV continuity you are looking for, but then again that requires Rhino + T-Splines.
T-Splines currently does not use trimmed surfaces, but it places vertex points points into the same plane to give a smooth result.
Think you may find this interesting.

-Fredrik