When displaying a content on a display page multiple things can impact the end results, like the content length, the images sizes, etc. Page authors need to have a visual control of the display page in context of the created items to improve the overall page experience.
One example of this would be authoring a blog entry. Being able to author it while "previewing" the final look and feel as a page in the site can be a much better experience. Our current blog portlet authoring experience tries to simulate that, but is only an approximation.
Of course, the big challenge here for complex content like those possible with Web Content, is that not all fields of a structure will be displayed. A first step would be to just consider this a limitation of the "In-Page Content Editing" and ask authors to use a provided link to the "Form-based Content Editing" for those extra fields.
The goal of this Epic is to visualize the Display Page Template in context of the item types (e.g. Blog Entries) so that the Page Authors can control the Look and Feel for the content they are about to publish.