Steve L. I definitely believe in doing the best you can within reasonable bounds of time and money to protect myself and others. In general I am careful.
I've wired three houses and three trailers without any issues. Actually replacing a single breaker with a double breaker in an old trailer may actually be a safety improvement.
A box with a main breaker is easy to install and if one is installing a new breaker panel, certainly get one with a main breaker if you want one. Personally in our Scamp
16, four breakers has been enough with out a main breaker. Can I think of scenarios where another main breaker would be advantageous, be more protective? Certainly!
I think my single axis trailer, though we've never had a problem, provides a higher vulnerability upon tire failure.
One can reach a point of over safety.... I notice that a high percentage of children do not have the freedom I did as a child, everything is more guided, more overseen, more controlled except for drugs, alcohol, and ..... Just a thought.