[Plugin Request] theme's footer

Hi

The footer, which is displayed on the website, is always from the Theme (probably footer.php).

My question is: is there a way to change what is displayed in the footer, by means of a plugin? (I could just go and edit the footer.php of the Theme, but my boss doesn’t want that, he needs the flexibility to change Themes as he wishes)

Any help would be appreciated 🙂