I think the key would be to modify as little of the “edit” template as
possible, focusing on its partials. This was easy with
page_attachments, because I had to insert a partial, not modify one.
Perhaps you could focus on _part.rhtml and see if that will suffice.
Also be sure to make use of the ‘include_stylesheet’ and
scripts. These helpers can be called at any point – either in a filter
you add or in any view template/partial, as they are evaluated only in
the layout (which gets evaluated last).
There’s two primary methods of modifying the interface using ‘facets
lite’ - one is adding any partial above the button area (below the
tabbed page-part interface). The second is adding fields to the ‘meta’
area that includes the slug and breadcrumb. The reasoning is that John
and I felt those were the two parts of the UI that people would need to
modify most - attributes of the page object and other, more complicated
controls. It was kind of a compromise from the infinite flexibility
that the ‘facets’ branch attempts to give you.
Hope that helps!