I've had both types of microwave venting and each has its pros and cons. But yes, it is quite possible to vent outside and probably worthwhile if you use it a lot as you do. However, you will get air in through the opening as well, contributing to heating and a/c inefficiency, and if it has a flap type closure it can rattle in the wind.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC