Wait, why are you talking about removing an ostensibly useful feature (declaring a mimetype in a paste for certain mime types) because the end result could land up in the users paste, where it could be pasted into applications that're not equipped to handle random assemblages of bytes, even though they are specifically written to handle random assemblages of bytes...
Wouldn't you have to remove ctrl+c, <right-click> -> <copy-image> etc. from the UA as well?
