Insulator, I think you know more than most on this subject and maybe you can educate me some more. I also wonder. Around here most builders quit using a foundation with a crawl space and either have a basement or a slab so it has been a while since I have dealt with crawl spaces. We always used to insulate between the joists and under the floors and under all the plumbing except the water and gas inlets and sewer outlet. The water inlet got it's own insulation. Where interior plumbing run under the joists, we ran the insulation under the plumbing and filled in the gaps so it was covered. Of course, with mobile homes and manufactured homes not on a foundation, they use that fabric with insulation that lays under and seals the entire floor from underneath and then they now recommend venting the edging going around the home crawl space.
I suppose your method would also work but then you can't vent a wet crawlspace. Following your suggestion, I would also put down plastic and insulation on the ground just like you would on a basement floor. I know some of the old traditional methods have changed with new research, is this the case here? Thanks.