Additional email footer info

It appears that all the email templates in ZC each use their own code and apparently don't share a common header or footer like the page layouts do. From this I gather that if I wanted more info present in the footer I would have to edit each template.

What I am wanting to do is include more information in the footer to comply better with the anti-spam initiatives. With each email that goes out from the system I want it to also include the date and time stamp info when the client signed up and also instead of just a contact email I want it to include a link to allow the member to unsubscribe without having to jump through hoops.

Can this be done easy enough to create a phpinclude statement in each of the templates and include a file named say email_footer.php?

Open to suggestions here.