I've never been in those in particular but have built some very simular. I would highly recommend requesting a window in the loft. A octagon shape awning window is great, can leave it cracked open all summer to avoid that closed up smell. That heat really holds up there and you'll want some cool air if heating with a wood stove
If you go that route I'd look at the floor system and see how many blocks they plan on setting it on. Then dig and pour Concrete sono tubes. Keep it up high enough to crawl under for any future plumbing and discourage critters from living under it. The sono tubes below frost depth will keep cabin level. Another option would be a product called Dimond Piers. Not my preference but saves on ground disturbance.
May want to check with your town as most have a rule that under 200sq feet needs no permits and won't be taxed. They assume it's a yard shed. I have one one property that has a 12x16 cabin, sleeps 5 if needed (12 pitch roof so a big enough loft for king size bed) and main floor has bunk bed with a futon couch bottom. Have a bathroom with shower. One wall of cabinets, sink, dorm fridge and counter top stove. I'll dig up some pics tonight, you'd be amazed what you can fit in a cabin small enough to not be taxed!
Sorry if this is a book- I'm killing time waiting for frost to melt off a roof so I can start work