I have a generic template file that I would like to be used for every page. I have witnessed a co-worker add a single parameter to either his local.xml or page.xml layout file that forced every page to use the specific layout file regardless of database values. He has since left the company so I cannot ask him how he did it. I have tried the answer as suggested in How to set a default layout in Magento 1.5 using local.xml? but that did not work.
How do I force Magento (1.7) to load only the template/layout that I want?
It is pity, but there is not just single option that you can use to be sure that all page layouts will use your templates, but you can apply your layout handle that will set your custom template in each of the page layout handles.
So in your local.xml there should be something like the following:
The first part of the layout update, creates your own handle, that sets template to root block. All the others are including your custom handle into different page layouts.
Enjoy!