I think better to create a new feature request and link this topic. Now that we’ve had the discussion the feature request will probably be clearer in its scope.
I think the feature request will amount to making it easier to use the underlying slots of a Parent layout, or HtmlTemplate, without having to re-add a Slot component every time they get composed together.
The team did explore inheritance as a way to do layouts, but ultimately decided that composing layouts was a better fit, despite the tradeoffs.
But that’s not to say we can’t improve things to reduce boiler plate.