a. launch an email service that runs off the space in your dropbox, or b. automatically create dropbox folders shared between all recipients of an attachment and automatically set permissions.
I can already use google's Drive storage for email attachments and attach a reference to the file.
Maybe GDrive lets you store those formats, but I've never had GMail offer that as an alternative. It just stops me from sending executables around even though that is an integral part of what I do.
If you try attaching any file above 30 MB in GMail, it prompts you to send it "via Google Drive" instead, and automatically uploads it there.
In Outlook.com (was Hotmail), you can send a large file by sending a link to a file in SkyDrive. You don't have to upload the file to SkyDrive first; it's just an extension to the "attach file" feature within Outlook.com.
GMail has a similar integration with GDrive.