What extras should I insist on in a new Class C

Here in Texas, roof vent covers allow one to have a vent fan run for air circulation. Having a Fantastic Fan with a rain sensor is doable... but you are trusting a $1 piece of electronics from China to protect tens of thousands of dollars worth of stuff.

One idea I plan to do is see about a roof cover, but add a filter, then run the fan backwards (so it sucks air in, rather than blowing it out.) This would create a nice positive pressure to keep dust out.