Isn’t it enough to replace the {{ page.content }} line with the actual template that renders the page?
For example, I render a list of posts with this macro. As you can see, it shows some metadata (tags, date) and the summary.
If I wanted to “embed” the actual post content on the listing, I would modify this “list all posts” template so that, for each post, it renders whatever is visible on the actual post page (date, headers… whatever).
