I think it would be a good idea to set up a database table that holds the users short-codes. These short-codes can hold greetings, info, addresses, opt-in/outs, etc as well as letting the user create their own short-codes with predefined settings.
This will enable users to place things like the permission reminder within their HTML design and any footer unsubsribes can be controlled at that point as well. Simply identify a type for the short-codes and you can control if its a drop-down list, dynamic info or just a static image, etc. Kind of like WordPress.
This will also reduce code being stored in the email itself which will free resources for your company to grow on. (: ))