I am wondering what kind of moderation tools would be needed.
On the top of my head, I'd say a trust-level system would be great, both for instances and users. New instances and users start out on a low trust level. Posts and commemts federated by them could be set to require approval or get deranked compared to other posts and comments. In time the trust-level increases and the content is shown as usual. If an incident occurs and content is getting reported, the trust level decreases again and eventually will have to be approved first again.
You can couple that with a reporting-trust-level. If a report is legitimate, future report will hold more weight, while illegitimate reports will make future reports hold less.