I know other timeshare/vacation club developers have done this, and I think if disney did, they would sell quite a bit....
I've stayed at an offsite TS, and then at the end of the trip was offered to buy into the TS, and the developer would take the money I spent that week renting and use it as my down payment.
Now that would be nice, imagine staying at Disney (lets say CSR), and you spend $1,500 for the week for the room, and then disney offers to use that same $1,5000 as your down payment into DVC. I am sure anyone on the DVC fence would jump on that offer.....
I've stayed at an offsite TS, and then at the end of the trip was offered to buy into the TS, and the developer would take the money I spent that week renting and use it as my down payment.
Now that would be nice, imagine staying at Disney (lets say CSR), and you spend $1,500 for the week for the room, and then disney offers to use that same $1,5000 as your down payment into DVC. I am sure anyone on the DVC fence would jump on that offer.....

I seem to remember being able to get a credit for part of your vacation costs to be used towards 
