I could be wrong, but I'd suspect people needing to upgrade or downgrade the size of the room they request isn't that common, especially when it comes to DVC members, because let's face it, we've got tons on the ball.
You are talking about one of the busiest periods of the year, so that definitely makes it difficult to make changes. Even at SSR (also my home resort) which is ginormous, but not everyone's cup of tea, which means if you can't get what you want there, you're pretty much S.O.L.
To maximize your point value, I'd suggest trying to do this:
-Anticipate keeping the first part of your reservation no matter what - 3 nights in a 1BR in SSR. And prepare for the likelihood that, no matter what, you're going to move at least once
-Try to get only switch your reservation for the rest of your trip - 6 nights - in a 1BR anywhere else, including OKW. OKW, along with SSR, have so many rooms that they are often your best shot. Pick the order of resorts, from most to least desired, but keep OKW in the mix. Even though technically, once on a wait list you only get what you want if everyone on the wait list before you gets what they want, you never know if you may get a sympathetic agent at the exact moment someone cancels.
-If that becomes too trying, try to get a 1BR for just the nights in which you currently have the 2BR unit. This means you'll be switching 2 times, but at least you won't be wasting points in a 2BR you don't want.
Worst case scenario, consider this: 2BR units are usually 1BR and studio rooms opened up with a connecting door. Specifically request a "lockout," then see if any other friends or family may want to join you for just those 4 nights. In a way, you have an advantage - you definitely have a room at WDW during Thanksgiving! Some family or friends may be willing to pay you to share your room, which, while it doesn't compensate for the use of points entirely, may at least take some of the sting out of using them (and give you money towards meals or souvenirs). If you get a "lockout" 1BR/Studio combo, those friends will essentially have their own room. If it winds up being a dedicated 2BR, it's not that big of a deal, they'll still get their own bedroom and bathroom. If there's a coworker or neighbor you can tolerate for a couple of nights, ask around and see who bitea at the chance to see WDW during a major holiday, while it's already decked out for Xmas, when the room is already booked. Hell, some people might consider that you've done them a favor! The only caveat is that it's only fir part of your vacation, so they can't arrive and leave with you, unless they opt to get lodging elsewhere when not with you.
Either way, I'd suggest you request a "lockout." At the very least, you may get lucky, and when your 1BR becomes a 2BR, they'll just open up the connecting studio; this way, at least, you don't have to move.
