Add "attribute" type to Customizer Smart Field

Is it possible to add an attribute option to the edit menu on the customizer smart field?

My use case is that I want to use a srcset picture element to display my logo in a WordPress theme where I have a default SVG logo with a PNG fallback.I can use the image option to easily set the PNG version either with a custom customer item or the default WP logo, but I don’t see a good way to add sources since I can’t set attributes.