Using a hard drive would be bit of a pain due to the extra bulk. You would be better off using a jump drive for your extra storage since you wouldn't need to worry about additional power. This goes with any tablet, including the Nexus 10.
However, after reading your initial post, I don't think you would even need additional storage. I have had 2 seasons of Dr Who along with tons of apps and a couple dozen games (many of them pretty large). Right now, my storage is 11.72 GB of apps (mostly games), 2.8GB of pictures and videos, and 256MB of music. I have never had to delete something because I was running out of space. Once I have watched a video, I delete it and load them as needed.
Unless you are trying to load entire movie collections on your device, space won't be an issue.
However, after reading your initial post, I don't think you would even need additional storage. I have had 2 seasons of Dr Who along with tons of apps and a couple dozen games (many of them pretty large). Right now, my storage is 11.72 GB of apps (mostly games), 2.8GB of pictures and videos, and 256MB of music. I have never had to delete something because I was running out of space. Once I have watched a video, I delete it and load them as needed.
Unless you are trying to load entire movie collections on your device, space won't be an issue.