I think you're underestimating just how extremely unprofitable NPS is. Nobody but a complete sucker or die hard altruist would join a private partnership with

I think you're underestimating just how extremely unprofitable NPS is. Nobody but a complete sucker or die hard altruist would join a private partnership with a national park... though the most likely outcome would be that someone would find (or intentionally insert) some loop hole to exploit natural resources within the parkland and just turn it into resource extraction. Alternatively, I suppose you could make it so severely exclusive that you could turn parks into an exclusive resort for the super rich and start charging outrageous sums to visit them while pulling down your maintenance costs to just some luxury spa. Either way it'd be awful and likely just lead to bankrupted parks in disrepair.