I've started work on a MOD for this which will be a complete replacement for the username field in basically all front end screens.
I'm probably 50% done and will post up some screens when I get a chance, but there are many code changes to do.
Will have similar ACP functions to allow, disallow usernames as well as admin ability to change display names or search on the display name as well as the MCP, any changes will also appear in logs.
On registration a display name will be required and users will log in with their username. On all other screens, the display name will be shown to the user.
Formerly known as xceler8shun