I would have to agree with others about the 12 VDC microwave, the power draw on batteries would be brutal. Although I have a microwave built into my CT conversion, I don't really use it that often and would probably not miss it (Oh, who am I kidding- I am never going off the grid!)

It is used mostly for reheating my cup of coffee, I should drink it faster.
Since the topic has changed, evolved? degenerated? I have used both the Coleman skillet

as well as their slow cooker.
The skillet is a joy to use. The slow cooker, not so much.
The major problem with the slow cooker is that it isn''t. The flame will not idle down low enough, the flame is too close to the bottom of the cooking insert, the insert is too thin, and the area that the flame covers is too small. All of which combines to make cleaning up after a pot roast a hour-long job to get the burnt gunk off of the bottom. And that is using determination, and about a pound of elbow grease. After making and riveting a flame spreader to the slow cooker, similar to the one found in the skillet, the results are much better, but you can still write home using smoke signals.
Ideas about using a crockpot insert over a flame will probably result in exploding stoneware. The liners are designed to be heated slowly and over a wide surface area, concentrating the heat to just the bottom could unduly stress the ceramic.
I would probably use the old, but tried and true dutch oven, on the coleman stove. I can make sauerbratten in a cast iron dutch oven over a very low flame, letting it cook for hours without burning.