Safety and common sense
I can see that there are varied opinions on this. For myself, facing a very similar set of circumstances as the OP, this debate was educational. While I won't bore anyone with my electrical qualifications, let's just say I know my way around a wire harness.
My general mindset is to over engineer, mostly because I have seen the results of the "just meet" the standards and criteria mindset as well as seeing the other side of this where systems were designed to exceed the environment of use.
From experience, I prefer the exceed criteria.
For me, My RV is an investment. I'm looking at the long game. My RV is 32 years old this month (Mfr date 6/86). I plan to have it for the next 20 years.
Additionally, I want it to be safe and secure. I neither wish to put myself or others in danger. My life is worth the $200 for 200' of the ancor 12/3 wire spec'd in a previous post. I believe your life is equally valuable.
As a rule, NFPA standards are written in blood. For me it's even more personal than that. I have a nephew who is a NY fireman. I would hate to have to explain to him why my TT caught fire or to the Mother/brother/sister/grandfather of one of my guests why little Johnny was electrocuted/burned/suffocated.
I prefer to believe that none of you wish to be in this situation either.
Thank you uncle bob for posting those standards. RVIA has a new member and some of the publications mentioned are now on their way to me. I only wish they came in PDF format.
Warmest regards to all
Hector (Formerly KA2AKR)