The first two links are basically "nice" versions of the 3rd world rocket stove mass heaters. I'll probably go with the nicer version. I always wonder why people don't allow for air from *outside* for combustion air, it makes the most sense. Why would you pull air from inside to burn and force cold air to be drawn in from all the cracks and so-forth. Not to mention cold air is denser, more oxygen, for a hotter burn.
And for code in northern Michigan, in the woods (the big woods), it's pretty lenient. As long as I feel good (as a licensed builder and licensed electrician) I should be good.
I wonder where you can source all those sweet oven doors and all that cool iron work, need to start looking.
Happy new year by the way. Seems a lot like last year, 'cept I gotta start paying FICA again so it's actually worse than the end of last year. Great.