An awesome idea!
I have a couple of large boxes of old power supplies, from discarded/broken/obsolete electronics gear. Whenever I find a need for a replacement power supply, or some potential application for a voltage adapter/power brick, I shuffle thru the boxes and see if something there will do the job. This usually entails getting out the soldering iron, and fitting a different tip. Way better to have standardized tails on the units, for sure!
What we need now is the EU to take the initiative and mandate it.
Of course there'll always be an worm in the Apple (pun intended) - where a manufacturer insists on a proprietary standard. See the new iPhone for instance......