Sites upgraded from 6.x don't fix tokens in autosent messages

When you upgrade a site from Drupal 6.x to Drupal 7.x, the messages sent to users (under Configuration > Account Settings) remain the same. That makes sense, generally speaking, except for two things:

1. The format for tokens has changed. What used to be !username is now [user:name], for example.
2. There's no replacement for !password.

As things stand now, nonsensical emails are going out to users with the unsubstituted tokens in place.

On one hand we want to reduce the number of things upgraders need to fix in their 6->7 site, so this really should be fixed. On the other, we want to avoid changing custom texts administrators may have put in these messages, so we shouldn't do this with a heavy hand. Complicating matters, there may be some reason the !password token has no new version -- I don't know.

So here are my recommendations:

1. Automatically replace tokens with their known replacements during the 6->7 upgrade process.
2. Do [something] with that password issue. Is there a reason that token's not available in D7? (I don't understand it myself.)

Good luck!