To me there's two big examples of hive minds that stick out to me in Sci-fi.
Things like the Geth, where they work as a hive mind but can generally work with other races despite this. They're not really evil and purgy.
Then there's races like the Borg, or Tyranids where the only thing IS the Hivemind and everything else is just resources.
So there should be a Hivemind and Fanatical Hivemind like the other Empire Ethos. Maybe let the normal hivemind pick one other ethos that's not on the Authority line as well?
Things like the Geth, where they work as a hive mind but can generally work with other races despite this. They're not really evil and purgy.
Then there's races like the Borg, or Tyranids where the only thing IS the Hivemind and everything else is just resources.
So there should be a Hivemind and Fanatical Hivemind like the other Empire Ethos. Maybe let the normal hivemind pick one other ethos that's not on the Authority line as well?