Cisco AAA/Identity/Nac :: Manipulating Username In ACS 5.3

Does ACS 5.3 has a feature to allow you to change or otherwise manipulate a user-name value within ACS as an authentication request comes into the system.
 
We want to use ACS to authenticate users to a particular device, but the device does not allow us to have username's in the format that we require, and the rest of our systems allow and require.
 
We want a way of manipulating the user ID of someone logging into the system, so that when the authentication request hits the ACS their username is massaged into the format we require, before being further processed against identity policies etc.