" I think, a maximum of 14 days within a calendar year would be fair. Of course, if you did that, some people would reserve under other names, which would be a rules violation."
NPS fixed that by requiring a photo ID to check into a site. That also fixes the problem with people selling reservations. The main problem with that would be coding the database to show how many days someone had camped there in the year.
The problem in the Keys is that there isn't any place to build new parks. Land down there is very very pricey, no surprise. Also my guess is that FSP are one of the few in the US that run in the black on budget.