Marylyn,
As an MVC owner you already know timeshare is about destination travel plain and simple. Marriott has a fantastic product, though it does carry a premium price. Still, it's flexible enough to meet any need and you can go developer or resale.
You're experienced enough to know that Marco Island is going to be a fantastic resort and that the resale market will be nil for a few years. As you say, you've got to pay the man if you want in now. Part of the TS paradigm is when you purchase. If you purchase straight from Marriott pre-construction or early in the life of a resort, you should be able to recover your purchase price if you allow enough years ( and usage ) to pass.
We ourselves own at Ocean Pointe, Playa Andaluza, and Marbella. We bit the bullet at Ocean Pointe (Plat) & Playa (Plat) because we wanted in early. We didn't get those amazing deals that pre-construction purchasers get, but we bought early enough to have already hit break even when/if we sell, even via Marriott. We pick up the Marbella Gold last year on a financing deal similar to yours, but in Europe we got about 6% for a 12 month loan, so we've got 6 payments to go and we're done ( earning MRP with each monthly payment, but no bonus points ). That Marbella week came with an EY point option and we'll either use it as a MRP ATM machine, or we'll use the week in the fall.
I think that you're an example that resale is a thrifty way to build a portfolio, but there are also times that developer is a good option. The hardest part for you will be waiting out that first year for occupancy.
Actually we're in Playa Andaluza right now having a blast. We did our owners presentation and got some more MRPs and a Euro Marriott bonus bucks cert that we'll use in London in the fall. Life with Marriott is interesting indeed.
Barry