Solved
Delegation Pattern and Sightly
I am implementing this within my solution: Delegation Pattern for Sling Models · adobe/aem-core-wcm-components Wiki (github.com). I'm inheriting the core Image component and extending it with some additional properties and markup.
Within Sightly, is there a way to just render the delegated component?
For instance, I want to do something like this:
<section data-sly-use.custom="...">
<h1>${custom.someProp}</h1>
<!-- render injected delegate here. In my case, it's custom.image -->
</section>