When using the Google Drive integration for Mac OSX it would make way more sense for the attachment to link to the local copy of the drive file using OSX's file URL scheme. In that case, if you're offline then the Google Drive links would still function. Also, it's just more OSX-like. And there's the advantage that the file will open with the user's preferred app. Some files may even be unreadable by Google Drive.
Please consider adding this as a feature. I really appreciate what you guys are doing with the Google Drive integration, but I think it could be better and right now it's not qu