A first step is RBL intergration, a shared blocklist of spam instances that subscribed instances would use to blackhole spam users/traffic/instances. These are used ubiquitously in email spam systems, so there is a precedent in federation systems for it working. We need to stand up an RBL, and then mod Lemmys federation system to work automatically based on the community blocklist.
It does mean that poorly admined instances will get blackholed, breaking their federation, but that’s the cost of a healthy network.
Self hosting and syncing data to a 3rd party would give you total control of your data and data resiliency.
Sounds like a good combo that’s lacking now.