Rick,
Might you be willing to make it optional that a board could be set up so that users log in with their e-mail addresses instead of usernames? It would still use their usernames etc. once they logged in.
After struggling with the issue for some time, we moved our sites to use e-mail address for login a few years ago (as more and more big sites do).
Now, we tell people that they have to log into www.* with email/pw and forums.* with username/pw.
We do have a continous stream of senior (older) users that seem to get confused by all of this.
Thanks for considering it...
Greg