For the 4-patch center you can create your 4-patch then put it on the pattern as if the center was just a square. The diamond sections I’m really not understanding. Is your paper piece pattern numbered/ lettered to show the order to apply your pieces? If not I would make an extra pattern then cut it all apart - number how it goes back together. I’ve done literally hundreds ( maybe thousands) of paper pieced blocks- I’ve never had one need a y- seam-