The z rest is dirt cheap and light weight. It's not as cushy as one of the inflatable ones, but it won't "pop" either. The key thing is insulating you from the ground since your weight will crush the sleeping bag insulation under your body. That said, a thicker self inflating version might be better if you don't sleep well without some padding. Like x SF med said it's your choice but make sure you have something for insulation.
Also, looking at your list, why bother with boxers? Long underwear would be more important in my mind. Also, for your sock plan, my thought would be to reserve the third set as a pure spare and switch between #1&2 day to day, wear for a day then rinse and clip to outside of pack to dry the next day, etc. As to clothing, I'd rather have a light weight gortex outer layer than a poncho. It would change your clothing plan a bit, but I'd rather be dry at the end of the day than the mix of condensation dampness that a poncho has always brought me.
In any event, I'd build your plan then do a couple of long weekend hikes using your exact plan to see how it feels; with a constant eye towards what can I cut out and make this rig lighter?
Have I mentioned that I'm really jealous that you're in a place to actually do this?
Also, looking at your list, why bother with boxers? Long underwear would be more important in my mind. Also, for your sock plan, my thought would be to reserve the third set as a pure spare and switch between #1&2 day to day, wear for a day then rinse and clip to outside of pack to dry the next day, etc. As to clothing, I'd rather have a light weight gortex outer layer than a poncho. It would change your clothing plan a bit, but I'd rather be dry at the end of the day than the mix of condensation dampness that a poncho has always brought me.
In any event, I'd build your plan then do a couple of long weekend hikes using your exact plan to see how it feels; with a constant eye towards what can I cut out and make this rig lighter?
Have I mentioned that I'm really jealous that you're in a place to actually do this?