I can not see the point of your method cranial-bore. If you need to write the title etc. into a variable on every page why not just do it in the header anyway?
If you decide to change the title or metatags on more than one page you need to open every page rather than do it all in one place.
But the titles are supposed to be different on every page. So saying you need to open every page is true, but logical. If you needed to change the content for your whole site, you'd need to open every page too. I don't think there are practical benefits to defining every title and meta description for your whole site in one file.
Bookmarks