Parking brake - option
There are all kinds of things you can put in a RV. They all tend to add weight, complexity, build time and cost. These nice to have options sometimes can be a source of maintenance problems and extra failure points. Dan's been flying his RV about 500 hours and used it once. I can only remember once in 20 years of flying that I was worried about parking due to winds, where the parking brake helped. The idea is if you are going to leave your airplane it should be tied down, blocked or in a hanger. I will not be adding this option to my new RV.
Keep it light and simple and pick the options carefully. George