Of course I can put a global flag for swapping header content to footer content and vice-versa. But what if I put the non-recurring "motto" of my previous example in a recurring footer and preserve easy swapping? I would have to do something like this (pseudo-code), in order to swap:
header-content = page-numbers
footer-content = motto-on-first-page
header-content = nothing
footer-content = motto-on-first-page + page-numbers
As you can see this is not a simple swap: additional logic is required, because motto and page-numbers have two different recurrence settings (no recurrence for motto and recurrence for page-numbers). This happens because I'm coupling what should be in the body with what should be in the footer.
Instead, a clean or basic template IMHO doesn't need additional logic: just set the recurrence values for the header and for the footer and you have done.
And this is how, AFAIK, a basic typography template does work. When I write such a page with LibreOffice, I don't need any additional logic or plugin for swapping the elements. In addition: It is true that a footer doesn't necessarily have to be recurring; however, as you can note, it is recurring as *default*. This default has a precise meaning: recurring is the rule, non-recurring is the exception. When you have to use an exception, you should firstly evaluate if you have a proper field for managing it. And the proper field for this case is the Body part, which is non-recurring as default. This is why I would use an alternative tool for cover/introductory pages of a score, in case they don't fit with the LP template. And this is absolutely not intended for "blaming" LP: instead, it is the contrary. IMHO, having an all-in-one program, especially for open-source programs, is not possible and it would not be reasonable either. LP is excellently focused on score engraving and that is enough. All-in-one programs are better for closed source stuff, not for open-source systems. And putting together different open source programs so to have an exhaustive system should be a normal routine. Hope my message is clear.