You can immediately sync it to your device when you purchase. But of course that requires you remembering to do it. Annoying, but if you're online to purchase you can sync to device then as well.
I'm not sure there's a way for B&N to revoke titles either. The DRM seems to just be keyed off of Name and Credit Card Number. I may be a minority, but I have several hundred titles that fit with room to spare on one of the later gen Nooks. Now as far as getting an actual file.... Maybe you'll just have to get a first gen Nook. Surely the desktop application stores an epub locally at some point though?