I would strongly advise against just ignoring code. some things are there for a reason, and getting homeowners insurance could be near impossible then. I'm designing a house myself and the first thing I did was read the international building code, which is the most basic one applied to this country. I admit I didn't pay much attention to the whole material part since i'm going with a traditional, if heavily insulated, build. Most basic takeaways: bedrooms have to be at least 70 square feet, no shorter than 7' on a side. window/glazed surface has to be no less than 8% of a room's square footage, with at least 3% openable. there are various limits on lighting as well.
Personally, I don't think
I'm going to get insurance on my house after its built, unless its required for my mortgage
or something. With how little most tiny houses cost, if you put money into a savings or invest it instead of a monthly payment, you would soon have enough
to entirely rebuild if needed.