This addon will change the default behavior of the Guild Window to filter by Online Only the first time you open it. You can see Offline by selecting the Offline checkbox as normal.

Note:Version 1.0 doesn't change the default behavior of the checkbox to be checked, so when you first open your guild window, you will se"Show Offline" checked, but the list will only show those guild members online. I'm working on figuring out how to uncheck that box by default. (Anyone who knows how to interact with the default UI, please shoot me some links? Thanks)