I have repaired an old quilt that my grandmother made around 1900. I re-enforced the fabric with new fabric where the old fabric was coming apart. That quilt had really been used a lot! I have it on a guest bed, but every few months I find another hole in one of the pieces of fabric that I have to applique a new piece of fabric on top of. So far I have been able to almost match the patterns and colors well enough so that the repairs aren't very evident. My point in sharing this is to tell you that if you keep the old muslim (which is thinner) your quilt will not have a useful life without a lot of repair work. Consider how you will repair worn holes in the muslim as they appear after you have applied bridal illusion to the quilt if you plan on using the quilt and not just displaying it.
Bridal illusion is used to make veils for brides and is available at all shops where you can buy supplies to make veils and wedding dresses.