Yes, you can rent points and use them for a Disney Cruise. However, from what I've seen it looks like it would be cheaper (maybe much cheaper) to pay the cash rates. In fact, I'm thinking about doing the opposite of what you want to do. We are talking about renting away some points in order to pay cash for the cruise because it seems like that is a much cheaper alternative.
OUr points are usually valued at somewhere from $3-6 by Disney when you take the rack rate and divide by the number of points. It would be kind of like me selling you $5 bills for $10 each for you to use to pay for something.