One of the most astounding reversible quilts I ever saw was a log cabin by a Japanese quilter at the Houston International Quilt Festival years ago.
How she ever keep the two sides - which were two different blocks - in mind I'll never know.
It must have been like backing a trailer, patting her head, and rubbing her tummy all at the same time!
This was pieced in a Quilt-as-You-Go method that I later learned from Karen Stone. It's surprisingly simple though a bit time consuming. When the block is done, it has also been quilted, so there's no need to do more when the top is assembled. Not sure I can explain it here in words; it's a technique that is much easier visually done. Surely someone has written a book or tute on it by now.
Jan in VA