yeah... but... i've got 70 friends in messenger... and it would be BORING to have, each time i change my font, to tell everyone to install something...
And it wouldn't be a "major breach in privacy" imho... because when you send an image... there's a little "preview" and how is it in my pc??? there's a temp file that has been created!!! WITHOUT ASKING FOR MY PERMISSION!!! HERESY!!!
j/k... honestly I don't think it would be a problem ...
but if you say that this function could be used also like some kind of powerful and dangerous "overfilling HD's" tool, I could answer that it would be easy to create some kind of "font number limit"... like... one per contact... (in order to prevent "overfilling")