The most important thing to consider, is that the campsites are not part of the Disney Vacation Club.
DVC members currently have the ability to use points to reserve campsites, but that's a perk, not part of your membership. As with all exchanges, there's also a $95 exchange fee that is applied when you make the initial reservation, and again for any subsequent changes to the reservation.
The ability to use points for campsites, and the point cost for those campsites, is negotiated with another part of the Disney company on an annual basis, and is subject to change or being discontinued at any time.
Keep in mind, also, that you would need to purchase direct from Disney to use your points at campsites; resale contracts don't have access to the Disney Collection (non-DVC) resorts. That would mean you'd be paying the highest possible price for the contract, and that if you decided after purchase that it wasn't a good value and you wanted to sell, the price you'd get on resale would likely be far, far lower than your purchase cost.
So, in short, no, I couldn't recommend purchasing a contract just for use at the campsite.