It's a very simple but very useful hack. Believe it or not, I had a member on a forum that I go to (but I don't admin, sadly) who commented that something like this would be quite useful.
*Hits Install*
EDIT - You might want to note that, if a user is using the `postbit_legacy` template, they should edit that instead. I know it is pretty obvious, but, in my years of software development, I've met some pretty idiotic users, and it is better to be safe than sorry.