If it is of help, I use Active Directory as a simple Database from which to extract User Name, Mobile Number, Email Address etc in a small scriptlet as part of the login. It generates HTML, RTF and Plain Text versions with both Main and Reply Signatures based upon this data and puts the files in the Users default Microsoft Signatures folder. I also check to see if MS Outlook is installed and write the necessary font and signature values to the registry to save the user having to actually select a signature.
As it is AD based and in the Login script it can be centrally managed and updates every time the user logs in.
If it is of interest I will post the core of the script for you ?