Centralized Email Signature

We want to be able to centralize and control what email signatures are used for all our employees. In order to do this we want to be able to create a word doc with the email signature in it and store it on the server. Then when a user creates a new email message it pulls this signature from this file and puts it in their email before they send it. Is there a way to override the default signatures that users have and replace it with this signature using VBA? The only problem is that the signature in this word doc will not have their name since it will be a centralized signature so I would need to pull their name from Active Directory and place it on the top of the signature. This signature will have font colors and a jpeg file so it would need to be created in HTML formatted emails only. That is the default format we use anyways. Any ideas on how this can be done?