You say you have an embroidery machine. . . what if you had fun with that. Do enough stitch in the ditch and block outlining to make it pretty stable, then can you do some fun tone on tone embroidery motifs? Playing on the envelope / mail idea, what if you did some faux postage stamps or seals, or phrases, like "sealed with a kiss", "air mail," "do not bend, spindle or mutilate". By keeping your embroidery thread matched to the background, it wouldn't totally overwhelm the quilt, but it adds a fun and creative touch, and I'd think it would be fun to do too -- taking the dread and drudgery out of this step of the process.
Either that, or find a quilting buddy who loves doing the quilting step and trade off chores with her/him. I love FMQ so I do a lot of it for friends, if they help with some of my ironing, stretching and basting, tidying up.