Grease Pencil Interpolate tool

The new Interpolate tool for Grease Pencil 2D animation can interpolate between a stroke selected in one frame and a stroke selected in another frame. That's really neat but the fact that it has to interpolate between whole strokes, is limiting. It would be nice to be able to select parts of strokes in one frame (point to point) and another frame and interpolate between this stroke sections (not whole strokes).