The Rangers seem to exist in... deniability (spelling?), for lack of a better word. It wouldn't surprise me if the Liandra gets sent on the most deniable missions -- the ones where it wouldn't be so terrible if they didn't make it back.
I'm not saying the Rangers would throw the crew's lives away; but somebody's got to do the suicide missions. And with such a compact crew, well, I guess it makes the sneaking that much easier (depending on the Liandra's stealth capabilities, shielding, etc.).
Besides, the most dangerous missions make better action stories!
So will it be Scully and Mulder on Mission: Impossible?
As to the Enterprise D, I think the crew compliment was 1,200 or so -- including families.
Adding families was a "humane" move, helping families stay together and letting parents help raise their kids, etc. Granted, being separated from your family is very painful; and leads to resignations, family breakups, etc.
The removeable saucer section was their response to safety considerations. All in all, I think it was just a construct to bring us Wesley Crusher.
It also shows how little economics means in the Trek universe. A ship like that would cost a fortune, not only to build but to operate (think food storage, spoilage, energy use, water & toilet use & storage).
Trek people usually respond to this with claims of limitless recycling and matter/energy conversion. Well, it's their universe, so I guess they make the rules. But given the number of bad guys out there, and that a smaller ship would be just as powerful and capable of longer missions (i.e., just leave out the families), and would take nowhere near the time, people, materials to build...
Second, saucer section notwithstanding, kids on a military ship is a needless risk. It certainly has to affect a comander's decisions in dangerous situations. It ain't the Love Boat!
Finally, that term... "starfleet officers..." Where are the enlisted people? Yes, they kept calling O'Brien "Chief," but he walked around for years with a full lieutenant's insignia. O'Brien aside, where are the working people?
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"What's up, Drakh?"
Michael Garibaldi