It's not immediately obvious, but you could create a custom element with Skate that takes it's content and creates a new custom element definition from it, similar to how Polymer 1 worked. This approach was discussed as being implemented in custom elements v2, but is closed to see what frameworks come up with: https://github.com/w3c/webcomponents/issues/136. This is totally something that could be done with Skate, though.