How would you filter out the offending MMS messages? People send legitimate videos as well; is the bug such that it's obvious which videos contain exploits?
It's also probably possible to extend the patches to detect malicious input.
Someone could probably also create a video with a payload to hot patch libstagefright.
This is brilliant. Assuming that it doesn't cause further problems.
Here's a more modest idea: Google should immediately issue update for Hangouts and Messenger app that at least disables automatic MMS retrieval. Many users have automatic updates for those apps turned on or maybe at least they'll see a notification about app needing approval to update.