Just to verify what you're referring to here. As opposed to the current Trim functions, that leave features intact, you want this function to trim the features at the edges of the polygon.
A couple of questions: what about splits, in particular when dealing with attributes. For example: if the polygon is concave and results in a line which bisects both lobes being cut in 4 places, creating 2 segments where there previously was only one. Should that generate 2 features, or a single multi-line feature?
Similar question for the Polygon case of this?
My first inclination would be to use multi-line or multi-polygon (as appropriate) in order to keep the features consistent.