Very clever. If I understand you correctly, the NeoAir goes above the Crazy Mat. That is interesting, in that, generally speaking, you get better warmth out of a NeoAir/foam combination by putting the foam on top. However, in the winter, when camping on ice or snow, I think foam on the bottom makes a lot of sense. In fact, it might make the most sense in the spring, when you might camp on melting snow, but the ambient temperature might be quite a bit warmer. Not only would this reduce the heat transfer down to the ground, but it might allow (relatively) warmer air to flow in through the sides.
For cold weather use, I've though about a foam envelope. Basically, it would encapsulate an entire NeoAir. I'm not sure how best to make it, though. I want it to be easy to roll, and easy to wrap around a NeoAir (or easy to insert the NeoAir into it). Incorporating something like this on the bottom would certainly lessen the bulk.