Reputation-based federation Instances you're closer to (interact with more) have higher reputation. Instances with users that your users thumb down/block a lot have lower reputation. Instances that are blocked by your high-rep instances have v low reputation. Once a low threshold is hit, admin is asked if they want to mute/defed from the low rep instance. Reputation isn't global, you can't measure the 'overall' rep of an instance, it's all relative to the instance you're looking from. Thoughts?
I am not totally in favor of this exact idea, but it seems worth thinking further about.
Oh yes I like that idea a lot, cross instance would be great!