microformats include pattern idea

The current microformats include pattern offers two methods — using <object> or <a> — to include in a microformat element parts of a document that are outside of that microformats element's DOM tree. Both patterns have problems, and have not been widely adopted. Also, the include pattern has not been updated for microformats 2. This page is a proposal for a new include pattern using a custom element without any semantics.

The tag name I'm using for the custom element in the example pages is <mf-include> but it could be anything. The custom element has a custom attribute includeid, but again, this attribute name could be anything. The custom includeid attribute would work the same way that the standard itemref attribute works.

Authors can use the new includeid to place a space-separated list of id attributes. A microformats parser should then search for an element whose id matches a token in the includeid. If it finds a matching id, it should include that matched element in the tree of the microformats element, as if it appeared in the DOM inside the <mf-include> element; also, the parser should ignore any content in the custom element, effectively replacing the custom element's content with the content of all included elements.

example 1
The first example is a page with an h-card element and two h-recipe elements. The h-card element describes the author of the recipes. Rather than repeat the h-card markup in each h-recipe, the page instead puts the h-card in the page <header> element. Each h-recipe element includes the h-card by using an empty custom element. A microformats parser should include the properties of the h-card as if that element appeared inside the custom element.
example 2
The second example is identical to the first except for one difference. In this example, the custom element has content, a shortened, simplified h-card. The parser should produce the exact same JSON when it parses the microformat, because the parser should replace the contents of the custom element with the h-card element. Using this pattern, authors can offer a backup for older parsers that don't understand the new include pattern.