I recommend these items:
Thermal cooker
Rocket stove
Solar oven
Bathtub water storage bladder
10 liter fermentation crock
Hand-cranked large quantity vegetable slicer/shredder
Well stocked field medic bag
I was looking for a way to cook without man-made fuel and was thinking rocket stove when I found the Kelly Kettle. Since my main interest is boondocking (dispersed camping) it really gives me a lot of capability but ideally you’d want both.
Your mention of solar oven also reminded me of the Omnia oven, which will allow you to bake using most any heat source.
The thermal cookers I’ve seen are pretty pricey, you can make your own Wonderpot for little money and end up with a non-electric crockpot. Most recipies only require boiling for 15 minutes and cook in a couple of hours.