But a federal setup that's concerned with maintaining the rights of its citizens would create a setup that would allow its constituent polities to defend themselves if the federal government began to behave tyrannically -- say, if something like Leyton's coup were to happen.
That's one way to see it - but the ultimate conclusion there is that every citizen must be armed to rise against his or her neighbor in case the upper levels of societal hierarchy don't please him or her.
And that dissolves the coherence of the society. A certain degree of oppression is always built into the very concept of having a society, and a certain degree should be accepted because the downsides of not having a society are so significant. If everybody were to be armed with the intent to disrespect laws other than his or her personal ones, that would make the society unstable. If every city were armed with the intent to only respect city legislation when the push comes to a shove, only nations with relatively few cities could remain stablish. If every state were armed, again it would be a bad idea to pool too many of these together because the more there are, the likelier that any attempt at pan-state legislation would rub some of the states the wrong way.
The Federation has something like 150 members, but definitely more planets than that. To satisfy the need for "local" armed forces, there'd have to be thousands of separate militias. How to legislate across all that, and expect the militias to comply? Either the general legislation would have to go for the lowest common denominator, or some degree of draconianism would have to come to play.
Odds are, if Leyton succeeded in his coup, even a unified Starfleet would subdivide by political view - but it would neatly split in two halves plus perhaps a few undecideds. In contrast, a collection of militias would have great difficulty in creating a unified front against the change in status quo...
Dunno. Somehow the idea of deliberately preparing the elements of a society for destroying that society sounds less appealing than the idea of keeping the means of destruction away from as many hands as possible. I know, I know, "If only the crooks have guns" etc. But in practice, the big guns are already in the hands of the people we trust not to be crooks (here and in Trek), and the little guns will never make a difference.
Except that there's never been any indication that the Romulans were a friendly government at the time
The very idea that Starfleet would feel up to taking on the Klingon Empire, or vice versa, suggests that the balance of power has shifted. And the simplest way for the balance to shift would be if the Romulans agreed to ally with one side (or more probably, with both sides).
Going from being chummy with Klingons to being chummy with Feds would seem natural. There were indications of a former, TOS-era alliance with the Klingon Empire, but we know Kor fought Romulans in the decade preceding ST6, and early 24th century will see the two species constantly at each others' throats.
and, plus, where are the Romulan military aides, if that's the case, to accompany the Ambassador?
It would seem rational for the Ambassador to be the aide. He could legitimately hobnob with the UFP top brass, as long as nobody spied into the actual discussions. ANd in any case, the show-and-tell for the President's benefit was not part of military negotiations and planning - it was the end result of that process.
1) The Federation Embassies on Andor and Betazed are historical sites that are no more currently functioning diplomatic missions
That would be a bit odd in the case of Andor, considering this world/culture was supposedly one of the founders of the Federation (although we still only have the word of an untrustworthy time traveler on that!). There'd never exist a time window for having a UFP Embassy on Andorian soil. Would work for Betazed, though.
OTOH, Cusack was actively working as an attache there, suggesting the "relic" isn't completely forgotten after all.
2) The Federation Embassies on Andor and Betazed are actually there to represent the Federation to foreign states that happen to be near Andor and Betazed but who do not themselves have permanent diplomatic missions from the Federation on their own soil.
Again possible, but Andor seems to be deep enough in the Federation core regions astrographically, and in the political dealings overall, that it's an unlikely spot for a "frontier outpost" of that sort.
3) The Federation maintains "embassies" on its Member States, and the definition of "embassy" has expanded to include governmental institutions that seek to promote cooperation and integration within the larger Federation government across the void of space. This may be similar to the offices that many US states have opened in the US Capital and abroad that seek to promote the interests of those individual states -- and federal offices located within US states that seek to promote the US federal government.
That would be my pick of the three. All the 50 States are still populated by humans, most of whom share a language or two. The UFP would consist of such a bewildering variety of biologies and philosophies that any attempt at Fed-level unity would need all the bureaucratic and PR help it can get.
Since Starfleet is more or less a military orginization designed to protect the United Federation of Planets, I'm sure each member world keeps their own "police force" of ships to deal with matters to trivial for Starfleet to get involved in.
But why would anything be too trivial for Starfleet? Surely Starfleet could operate those "police force" ships just as easily as anybody else - if not in fact more easily, as it knows a thing or two about operating ships.
If the idea of the military doing the policing sounds unappealing, just think of it the other way around: the police doing the military work. Starfleet would be lavishly equipped for both ends of the job spectrum, and for everything in the middle, too.
In the end, "concentration of power" sounds awfully hollow in this argument, because in practice "power" only comes from two sources: the barrel of the phaser, and the legislation that tells how the barrel should be pointed. There would be no difference between police and military in the first respect, as both could wield the same sort of weaponry if they so chose. And neither a separate police organization or one that is merely a branch of Starfleet would be able to budge legislation.
Timo Saloniemi