So, the basic situation is this:

I'm setting up a site for a client, and I have a given template that I've set up. It's got (for simplicity's sake) one "Page Placeholder" in it.

My question is this:

If I am using one template on multiple pages, without making needless ad-hoc copies of the template, how can I change which bit of content (read: sub-'page template') is populated into the placeholder?

For example, if I have my Master Page template, then inside of that can be either a "Front Page" or "Interior Page" template, how can I use a single "Interior Page" template to display multiple varying content displays? For example, if I want some to have a menu WebPart, and others not to, and another group of pages to have an entirely different menu WebPart.

The site-map calls for all these pages (or at least the parents of most of these pages) to exist in the site's root directory, so I can't set up some sort of sub-folder inheritance/population scheme.

Thoughts? Musings? Critique?

Just upgraded the install from 5.0 to 5.5.3789, if version matters at all to the response.