Oxide's trust quorum approach is also discussed on this podcast episode:

https://oxide-and-friends.transistor.fm/episodes/building-a-...

Is there any concern in this scheme with losing access to storage either temporarily or permanently due to losing access to key shares?

The bit I liked most is wrapping the old rack secret under a key derived from the new epoch so prepare can hand out shares without unlocking until commit

That tension between needing both secrets for ZFS rekey and only serving shares for the committed epoch is a real distributed systems headache and this is a clean way out of it