Lt. Boma from The Galileo Seven was a really strong character compared to most single appearance crewmen.
I noticed that Lt. DeSalle, who did become a recurring face, was added in the very next episode.
The production had also just lost Grace Lee Whitney.
Is it possible that they were looking for a new familiar face in Lt. Boma?
No way they would have written him so antagonistic to Spock if he was planned to come back.