Ah, so not part of the hotel charge, but separate fee you pay as you leave. That's how hotels in our downtown do it too.
Disney could do it this way at their resorts. Similar to city parking, instead of having the guard manning the entrance, have them at the exit. On the way in, people could scan their magic band, or if they don't have one they could take a ticket. Then, if they spend a minimum amount at the resort, they would be validated for, say, up to three hours. On the way out they would again scan their magic band (or produce their ticket). If ticket or band had been validated by a shop, restaurant, spa, or other service, and they had been in the lot no longer than three hours, they would exit for free. Otherwise, there would be an hourly parking rate. If the rate were something like 4 or 5 dollars an hour, I don't think anyone would mind paying that to take a look around a resort, but it would prohibit people from using resort parking as a means of avoiding paying parking fees at the parks.
Of course, I still think people staying at the resorts should park for free.
There are probably all kinds of problems with this that I'm not thinking of. Primarily, Disney wouldn't make as much money. But it would solve the problem of overcrowded resort parking lots, and make parking lot usage fair.
When I went to lunch at the Grand Floridan on Easter, I would have been happy to have paid for the extra time I spent resort-hopping, as well as for an hour of parking at the Wilderness Lodge. Ok, ok....I wouldn't have been "happy" to pay it, but $12-$15 would have been quite reasonable for an afternoon's entertainment and it would have felt immeasurably more fair than being expected to pay for parking at my future resort stays.