If you just want the display name to change..
Warning : Messing with the registry can break things
There is registry key that holds the names of Outlook profiles on a per user(Windows profile) basis.
HKCU\Software\Microsoft\WindowsNT\CurrentVersion\Windows Messaging Subsysytem\Profiles
You will see the profile names as reg keys here. I would recommend copying the profile that you want to rename to a new profile first using Outlook Control Panel Applet and then renaming the key. You can also modify the default profile entry to change the Profile that displays first (Saves you using the drop down every time) if you want to.
Cheers big ears