Quick way to switch between iTunes accounts in AppleTV

You can use separate iTunes accounts, but the HomeSharing account must be the same. You will need to authorize each other's computers/devices with both iTunes accounts in order to play back content purchased under the other account.

What I would do is:

• Have only 1 library
• Make sure that iTunes is configured to keep all your media organized (and point your single iTunes Library to your preferred disk)
• When adding files to your iTunes library hold down Option/Alt to let iTunes know that it shouldn't copy the file to where your library is

This way all your data will be organized by iTunes except for the large files that should belong on your largest external disk in the first place.

Cheers...