Does any one know whether it is possible to create one set of custom template files that will be applied across all active themes?
Case in point is I have the 133 theme pack installed (so 133 themes are active). If I want to customize footer.php for example, I have to edit footer.php in 133 places. I was wondering whether one can add a custom footer.php on one place, which would override the footer.php for each of the 133 themes without having to edit footer.php in each theme directory?
I found a way to do this for adding custom functions in fuctions.php across all themes using the "mu-plugins" (must use plugins) directory in the plugins folder as described in this post, which I found very useful. I was wondering whether there might be something similar for themes?
P.S. I am sure there are better ways of customizing the footer than overriding the template - this was just an example (I need to do far more extensive overriding of templates - mostly adding new ones, which do not already exist and I would prefer not to have to add them to each theme directory if possible).