The advance purchase for a multi-day discount on parking sounds like a great idea to me, as a predominantly off-site guest. Again, one would have to have access to data to work out how many days a typical off-site guest will spend on Disney property - then add extra days at a lesser or free price to encourage a further day they may not have visited the property before.
A good idea for sure - but Disney have the data. If the data worked in its favour, I am sure it is something they may have considered... On a personal level, I would definitely want to see this implemented.
Also, I'm not so sure about the idea of utilizing a state-funded prepaid toll system to pay for parking. For out-of-state visitors, it can prove to be a disappointment, as their home state's prepaid toll tag won't be accepted outside of that state.
As mentioned before, some parks offer free parking as part of your hotel rate or a vacation package. When I visited Legoland a few weeks ago, I noticed that one hotel (Park View Winter Haven) promised "refund on Lego parking" on their billboard. The billboard didn't specify if it was either part of the regular hotel rate, or part of a vacation package.
Otherwise, its just a hidden price in the cost of your ticket.
I think it was $6 the first time I came over, I see it's now $14 or $15 dollars, that's expensive!.