Stock Mail App - Outlook Sync, File As Problem
Currently there is no way to do this on an HTC phone. The People app from HTC will automatically display names as First and Last.

However if you connect the phone to exchange, as I have mine, then all Exchange contacts show up as Last and First, including in Mail and in People. So as of right now I would say if you can get his phone on Exchange, only display contacts from Exchange, and tell him to put them all in Exchange, then it should be a workaround to the issue.