Well, this is really none of my business
1. If the person already has a domain name why migrate over to Gmail and look for a "professional" username ? Don't most 'experts' on email netiquette say that it's more "professional" to have one's own domain than to use a Gmail, Yahoo, or Hotmail address ? Why not just switch the present domain over to Google Apps ?
2. What's wrong with registering their name at something other than .com ? Like: .net ? .biz ? etc. Then host with Google Apps.
3. For Gmail specifically: How about lastname.firstname @ gmail ? Or lastname.first and middle initials @ gmail ? Or part of the names (like Scott Johnson would become "johnsco @ gmail"). I believe those are considered acceptable and professional username styles. They may not be pretty, but then professional
looking usernames/email addresses usually aren't.
4. FWIW, I know Gmail is one of the few email providers that allow users to have a username that begins
with a number. Of course, that would be of more interest, I suppose, to someone who's not
using it for professional purposes (like: 2t_sweet; 2poor2care; 40winks; etc.). Not sure if there's a more professional sounding username that would start with a number, unless one would use a street address (123mainst @ gmail)....