The wait is over! With the next release cycle of Google Apps, you will be able to insert/attach any file up to 10GB in size from Google Drive. Rather than sending files which may exceed size limits on many email services, recipients receive a link and the ability to open or download the file via Google Drive (no account needed).
And, if you are sending a file to somebody without access permissions, the smart assistant will let you know.
For more info, visit the Official Gmail Blog.