One thing that comes to mind is that laser toner isn't water soluble, so if it gets "pushed" into the fabric (and especially the quilt sandwich) when the needle goes through the print of the design, and stays there when you tear the solvy away, you might not be able to wash it out of the needle holes. You'd have to try a pick it out.
For that reason, I would definitely test it extensively on a sample of exactly the fabric AND quilt sandwich stack you're considering using it on.