The backside of the chain stitch and the stem stitch are pretty much the same...they look like a backstitch. Herringbone, cross stitch, blanket stitch, and others have clean looking backsides as well. I don't see any reason why a small scale embroidery stitch wouldn't hold the quilt layers together just as well as a running stitch and be just as easy to needle as the tiny stitches done by accomplished hand quilters. Why not make a sample sandwich and try out some different stitches to get a better idea of the possibilities? I certainly wouldn't give up on the idea until you see how it works.
