You can set the email header and footer at template level. That would be applied to all emails based off that template, avoiding the duplication of elements.
It is likely we are visualising the same idea from different perspectives.
I am rewinding my thinking. What is the primary goal? If that is an email footer, say, containing the company address, phone, email and website, that information is suitable for a template. Theer would be no need to drop the same snippet over and over again.