I've been looking for a stainless basket to replace the biab bag for ages, and can't find anything the right size. I have a feeling that if the grains were able to swim a bit more than they can in the bag, I'd get improved efficiency, so a steel basket with a spindle down the middle from which mash arms are attached. Run it like a washing "mash"ine.
As a side note, I've also been wondering if applying a filtered suction pump to the grain bed might extract those last few points that inevitably get left behind.