It's not like buying a car. Its more like buying something at Walmart. Your not going to negotiate with the cashier at Walmart on the price of the fancy, Walmart branded toaster.
The answer will be a big NO -- they offer the price that they offer. There might be incentives if you buy a certain amount of points. So with that it doesn't sound like Riviera is right for you. On the resale market there is much more flexibility in negotiating prices so you might want to start there.
You might be surprised at the number of buyers who do pay "cash". It really isn't a big deal to them and as mentioned they make more off the financing. So it's more like they let you pay cash but prefer you wouldn't.
If the buyer defaults on the financing they get the product back and sell it all over again as brand new - actually for more than brand new. Cash is not king - Disney has lots of cash.