I was considering something like that as well, but I'm wondering if that would be beyond the capabilities of my hypothetical NE/SX hardware? The thing is that it would be at an angled view. I think that would be a lot of sprites, but perhaps if I were to make it more of a BG animation I could get away with it. I'd rather it was the drawbridge opening rather than closing.
Well, considering the NE/SX hardware...
SotN's door animation had like, 20 frames, whereas
CV1 had 3 frames. You could do something similar with the bridge.
Or as an easier solution, considering the wood is very old, it starts to fall apart as you cross it.