My husband isn't autistic but he likes heavy quilts. They are "comforting" to him so I can completely understand the theory.
My solution would be to use fishing weights. The little metal balls you tie or crimp onto fishing line to get the worm to sink down.
Another thought is to sew a large washer between to pieces of denim and make a raggy/shaggy style quilt.
The quilt would have to be hung & steam cleaned like draperies.