Ginger Spinner,
Once had a pair of Nomex burned off me while inflight. Hydraulic fed fire caused by some rather high speed FOD came my way. Six weeks waiting for the burns to heal. The places where the baggy pockets doubled or tripled the fabric had the lesser burns and the single thickness areas especially the area where the fabric pulls tight over the leg above the knee received the most damage.
Nomex has the characteristic of not melting like other man made fibers. That prevents the melting fabric from sticking to the skin and causing very serious problems after the fire.
I would suggest clean unstarched natural fiber clothing provides as much protection as does the Nomex. A nice leather jacket over a 100% cotton shirt and 100% cotton undershirt will work fine. Same thing for the trousers, 100% cotton or wool material would work fine.
Anything nylon, polyester, or other similar materials to include panty hose for the Ladies are killers during fires.
Nomex flight suits only work in flash or short duration exposure to fires. If you find yourself in a hot fire for any length of time nomex burns off like natural materials.
Given a Choice of a single safety device, I would rank them this way:
1- Helmet
2-Leather or Nomex/Leather Gloves
3-Above the ankle solid leather boots
4-Nomex flight suit
The helmet gives you a better chance to survive the crash, the gloves will guard your hands so you might be able to use them later, the boots do the same for your feet, and lastly the flight suit keeps grease off your clothes.