I'm working on a product, and I want to make pockets that look like this:

The angles on the sides and the length and width of the part is controlled by prompts, so this needs to be parametric. I can make a pocket with a pline machine token, but I need to tell it every point. if the pocket grows I cannot add every point to that pline to make this pocket work. If it was a square rectangular shape I could use the cutout 4 sides, but there doesn't seem to be any machine token for non square shapes.  Any Ideas?