That would be better than storing the messages in a mounted encrypted container (as I am 99.99% sure is happening now), but it is still no replacement for customers actually learning to use GPG. If the server becomes compromised in the future, newly written messages will still be vulnerable to plaintext interception. Using javascript for client side encryption in the browser would be an even better plan, but again it is no replacement for clients actually learning to use GPG and is weak to numerous attacks (plus requires javascript to be enabled).