I shared my thoughts in the other thread, but to summarize we have a way to manually deprioritize huge projects: this time we missed the alerts, but in the past the approach has been successful. Unless this starts happening consistently I'm not convinced we need to spend a lot of time on designing rate limiting.
The docs.rs team is also working on removing the blockers that prevent us from scaling the build system to handle the increased load. We don't expect this to happen instantly due to some architectural limitations, but we have a clear path on how to solve them!