Looking at Mark Henley's list, I am quite convinced its possible, though I'm not familiar with the conditions on the JMT.
That list proposed would be more than possible in South Australia on trails only such as the Heysen Trail, with predictable weather conditions in summer and known water sources every 10km. For that I would ditch the Tarp, Bivy, stove/pot/bic, windshirt, add some light insulation (a short sleeved thermal), and a couple of 2L platys and beef up the pack slightly.
I have been thinking in the last few weeks about something stupid like a sub 1kg (2lb) list for two or three day desert walking, with long distances involved (~100miles over 3 days) in Winter in South Aus. Trick is to do what the Aboriginals used to do and build a series of small fires around you and also warm up some rocks to go underneath at night. Temps at night in the middle of winter can get to 20F. Hard part is water (means beefier harness), and emergency comms gear due to the remoteness. I am thinking of doing something crazy like an ~2oz cuben backpack that will take gear, food and about 3L of water, and a tube arrangment to hold another ~4L of water across my front (like a sash from shoulder to opposite waist).
This is more about seeing the limits/honing skills for me, rather than speed/performance. I have NO DOUBT that it would be way more efficient for me to carry a more substantial, comfortable pack, and ~30oz of insulation, rather than going with the rather time consuming, uncomfortable fire option.
There is a certain "animal factor" involved when you go really low...