These are excellent suggestions, and I agree wholeheartedly. I think the main difficulty is in labeling “sibling communities” as such, because when you create a community, it’s not like you magically know which ones are supposed to be siblings to you.
What happens when you have two sibling communities that seem like they’re the same based on name and topic, but when it comes to moderation, they’re so different, you couldn’t really call them “siblings,” up to an including the mods from one not wanting to be associated with the other sibling community. Would there be an option to sever that relationship?