That is the reason for Comprehensive coverage.
What are they going to steal that is not replaceable? And if you plan on having non-replaceable items, go to a bank nearby and rent a safe deposit box. Obviously, you wouldn't feel comfortable with a safe in the RV, since that can be broken into or stolen also.
On most coaches, someone will have to pull up a ladder to go though a window, which would be kind of obvious.
A home security alarm can be put on your coach with 24 hour monitoring, if that's your thing.
Too many other things in life to worry about, so I say, much ado about nothing.
Maybe you could buy an armored truck and remodel it! :p