Some people that do alot of thread painting on quilts, put the top on the batt and stitch all the details. They put the back on later and just outline stitch the main designs. You don't even have to be careful of how far the quilting on the back is because the batting is anchored well with the thread painting. I think you could put a false back on your quilt, outline quilt the main parts to the front and put the binding on.