I’d engage the HHC CDR, show the counselings and the plan of action and how that plan of action isn’t working – ensure that counselings have been closed out, as well as any letters of concern. Naturally the HHC 1SG will also be interested in what this person is doing and if there’s any way to improve them/give them a chance to improve.

All your commander has to do, realistically, and legally is utter these words: “I’ve lost confidence in your ability to perform assigned current task/position”.

As the S1 you don’t appoint your NCOIC, your CSM places NCOs but the HHC command team have to be part of the conversation as well as your BN XO (aka. your boss).