Why not have this downloaded upon first use, the way that Flash and Silverlight have been?
Also, isn't this what users on many Linux distros (e.g. Iceweasel on Debian) will have to do anyway?
That's actually what we're looking at doing: the sandbox would be in there, harmless, by default, but the actual crypto module (the "CDM") would download from Adobe upon first need. (And they have committed to support the platforms we support, Linux included.) The exact UI is still up in the air. I could imagine us using the opportunity to display a message to educate users as to what DRM is and whose phone number to call if they don't like it. ;-)
Please do this!
I understand that Mozilla has been backed into a corner on this, so I get why you'll be adding this (much as I wish you didn't have to). But that doesn't mean forgetting about the issue entirely.
I wouldn't ask this of any of the other major browser vendors, but I like to hold Mozilla/Firefox to a higher standard. :)