Thanks for this response and, this is kind of what I needed to hear. Which is: “Its there and it /can/ be useful but its pretty fragile and your going to have to put a lot of energy in to make it work.”
Its not a critical need for me so I guess I wait until CRIU works out of the box. Although at this point (and given what you said about the linux kernel) an entire OS based on orthogonal persistence sounds more practical unfortunately. Not something LXD can really fix.