Just to expand on Crisi's excellent post a bit:
With DVC, you don't get your own membership in RCI. DVC holds the membership, and through DVC you get access to a limited number of RCI resorts. DVC is expensive, as timeshares go, even at resale. You're paying more for the access to the DVC resorts. In order to get a decent number of points to cover a DVC stay or a RCI trade every year, you'll be paying well over $10K to purchase.
Other very good timeshares offer you access to the full range of RCI resorts, and can be purchased at resale for a FEW DOLLARS. Really. I'm not making that up.
Would you rather pay $10K + for the privilege of trading into RCI on a regular basis, or a few dollars?
Now, that's certainly an oversimplification, but I do it just to illustrate what people mean when they say buying DVC to use for RCI trading is a poor value. As Crisi said, if you already own DVC, stay mostly at DVC resorts and decide one year that you'd rather trade out to the Caribbean, hey, that's not a bad deal at all.
But it sounds like you'd want to trade out at least as often as you would go to DVC resorts. That's where you'd be dramatically overpaying by buying DVC.
Many people here like to vacation at other places than DVC resorts, just as you would. What many do is buy just enough DVC points to cover their DVC stays (considering banking and borrowing), and then buy another timeshare that's a good trader at resale, for their other vacations.
If you do want to trade often, I'd strongly recommend that you consider doing just that. You'll save thousands of dollars, and you'll have a much larger selection of resorts to choose from.