Reverse screening sounds like the right call here. They're talking about 12 departures PER WEEK, so a maximum of 360 passengers per week. Realistically, given the planned departure times, you'd need to have two TSA staff onsite (at least) for about six hours a day during the week, and three on weekends. So, that's at least 72 staff hours per week, plus you'd need relief people most likely, equipment and maintenance, etc. etc. etc. That airport is just too small to justify a TSA presence.

Should be structured like Cape Air is at some smaller airports - arrive, get on plane, go. A number of smaller airports in New Zealand also have no security screening, and it hasn't resulted in mass carnage.