I would say then that you are lucky to do business in a city/state that doesn't require the Type 1 hoods. Even direct venting at times requires an exhaust fan and make-up air issues. I was trying to make the OP aware of the potential costs associated with these ovens. Budgeting $12,000 for an oven and finding out it will cost another $12,000 before you can fire it up is a sobering experience.
As for hand-built, brick and mortar ovens, codes must still be satisfied, easier to do in some cities than others. I think the costs of a custom build are of a different order than the pre-assembled. Just the structural loads involved require engineering, possible reinforced slabs/floors, etc.
If it's Pacific Coast Brick ovens you're talking about, they have UL listings. What other companies have you talked to that don't have listings either for the ovens or components?
The point I am trying to make is to go in with eyes open to potential costs. If you are prepared for the worst and end up in the best circumstances, then consider yourself fortunate/genius and move on. If, on the other hand, you've prepared only for the best case scenario and find yourself being dragged down by cities/contractors etc, then you will have to answer for your lack of preparation.