Well, in the case of DS9, yes, it would have made sense to split off Tactical and Station Security into two separate entities, given the nature of the setting, what with constant civilian traffic, legal problems, etc. that aren't necessarily a Starfleet or Federation problem, but nonetheless affect the residents of the facility.
I would think on a starship, though, that the two positions would be necessarily conflated, given that, with the exception of the Galaxy class Enterprise (which was as much a social experiment as a technological one), the vast majority of residents are going to be enlisted peoples for whom Starfleet security would be more than adequate to handle both shipboard issues and external threat assessment matters.
If anything, while we've been discussing people who didn't have business on the bridge, does anyone think that there were positions that SHOULD have been on the bridge that weren't? Or at least, like Engineering, have a ready place when necessary, even if the main officer in charge was usually somewhere else?
To me, it was always bothersome that there wasn't a dedicated Science officer in later series. Granted, in TNG, Data was the defacto science officer as well as Ops and Second Officer. As has been pointed out in the expanded universe novels, though, this was a unique scenario, given Data's abilities and not something that most starships could have gotten away with. Why is it, then, that it seemed like, after TOS, positions like the dedicated Science officer seemed to disappear?
Another that I would have thought would be there would be some kind of diplomatic officer. Not necessarily on every starship, but certainly those which, like the Enterprise, were expected to be in a lot of First Contact scenarios or be key vessels when dealing for foreign powers, etc. Granted, Picard could wear that hat when necessary, but wouldn't it have made more sense to spread the responsibility around a little more?
The more I think about it, the more I realize that the command structure on the Enterprise D was sort of precarious... The majority of mission critical duties were concentrated in the hands of way too few people, even among the main cast. Or am I just looking at this the wrong way?
Whose idea was that, anyway? Gene's?
