Re: Episode of the Week: The Arsenal of Freedom
Seems to have been a clear casualty. Data was apparently being considered for just the role, but then the creators got cold feet with too obvious TOS parallels and whatnot, and the unsatisfactory "Operations Officer" thing was invented instead.
We know from Conspiracy
that they had a science officer, it just wasn't a major role on the series.
"I had no idea you were so... formidable. " - Anan 7 to James T. Kirk, A Taste of Armageddon