Here’s how Kat Marchá describes caracoles:

"you essentially ask to join concentric federations of instances … with smaller caracoles able to vote to federate with entire other caracoles.

And @ophiocephalic’s “fedifams” are a similar idea:

Communities could align into fedifams based on whatever conditions of identity, philosophy or interest are relevant to them. Instances allied into fedifams could share resources and mutually support each other in many way"

The idea’s a natural match for community-focused, anti-surveillance capitalism free fediverses, fits in well with the Networked Communities model and helps address scalability of consent-based federation.