Best practice for page content across sites within a Network

Here's the situation: I'm setting up a Network, with custom theme, and I have some page content that I want to have linked on all the sites, but don't want the content 'in' a Page within the WP-Admin, for example a page linked from the footer, that may rarely change. I don't think I'm looking for a plugin to re-broadcast, but I might be wrong. I've been trying to get my head around the best approach.

I was thinking I could create a page-[template].php file that has the content in the file and then I pick that as the Page Attribute > Template for all the sites in the network. Then the sites can link to the page in their footer and if the page content needs to be updated it's a single update to the page-[template].php file. The drawback is the content is not in the WP-Admin and this most likely creates a duplicate content problem. I don't mind making updates to the source files for the Network and thought I could use a canonical link element to point at the main network's page.

Does this sound like an okay solution? Is there a step further I can go in the WP-Admin with this page that allows all the sites to use Network page and still be their own URL. I'm brand new to using canonical and networks, so forgive me if there is an obvious best practice. Thanks!