Lync 2010 sign-in address sadness

Lync at my company has historically been an application that IT folks use. Although I'm creating new accounts every day lately, most (80%) of our users do not yet have Lync accounts. We're Lync2010 on the server with the 2010 and 2013 app version on the desktop. Our desktops are pre-imaged by the vendor including the Lync install.

If the Lync client is installed on a desktop prior to the user getting a Lync account, the sign-in address defaults to samaccountname@domain.org. When I create a new account in Lync, I use the users email address which is first_last@domain.org. So we always run into this issue where the user will initially have an problem connecting in lync since the app is expecting a different sign-in name. Usually its a phone call to the user or a visit from our desktop team to fix the issue.

We would like to continue using the users email address as the sign-in address. My question is, is there a way (registry entry?) to force the lync application to use first_last@domain.org in cases where the lync account does not exist yet? This would save us the issue we're seeing that requires handson to fix.

Sorry for longwinded question...