Bechamel Mashed Potatoes

As the other 2 posters indicated, I don't know if flour will do your potatoes any good. However, a quick search brought up a Julia Child recipe using a bechamel. Go figure.

Agree with foodforthought that it might be redundant; unless you flavor your bechamel with seasoning such as nutmeg, the only thing you'll be adding to the mashed potatoes is flour (since most mashed potato recipes call for both butter and milk already). Even though bechamel itself is creamy, I'd be curious if this would translate well to the potatoes or if it would make them heavy and dense.
If you're thinking about this for Thanksgiving, I'd definitely try a small batch beforehand to see if you like the texture/flavor. And while you can make bechamel beforehand, you should place waxed paper or pour a small layer of milk over the top of it to prevent it from forming a skin while stored.

IMO bechamel sounds maybe a bit redundant though it does have some distinctive qualities that would make it worth a try. Would definitely do a test run before the big meal. A veloute (made with stock instead of milk) might also be a interesting addition. Yes, you can make the bechamel or veloute ahead of time. Stores in fridge for days just fine. I would bet it freezes just fine, too. You might also think about making your potato dish a day or two ahead then reheating in oven provided you have the oven/logistical capacity.