"For the second it basically doesn't work that way because trim boundaries don't control the surface shape directly, it's more like they live on top of the surface and mark which areas of it are active and which are holes."

If the shape data is retained when a portion is trimmed out of a surface (creating this inactive area you mentioned) Is there some kind of heal command that would remove this inactive area? Returning the surface to its full shape? I hope that makes sense.