a) shutter curtains move extremely fast. There's been decades of R&D and improvements to get them where they are today, they are extremely strong and light and there's no way you can just 'make' one.
but b) as far as I know, the only difference between a 645AF and AFD is in the way it communicates with the backs. AF bodies are relatively cheap compared to AFD because they can't take digital backs. For $3-400 you can get a working AF body, or maybe find a junk one with a decent shutter to swap out for $200. No idea how much a real repair would cost, but probably more than that.
Good luck.