Here's a basic comparison of the traits of each world/species (as we know of):
Coalition of Planets
-Humans: Explorers, diplomats, thinkers
-Vulcans: Thinkers, philosophers, semi-pacifists
-Andorians: Warlike, passionate, value honor
I think that those are gross over-simplifications -- stereotypes, really -- of the founding Coalition/Federation worlds. For one thing, you're attributing diplomacy to Humans as though it's some inherent trait. It's not. The rise of United Earth as a diplomatic power -- an "honest broker" -- came about specifically as the result of the efforts of Jonathan Archer and of the policies of Prime Minister Nathan Samuel -- policies that Samuel explicitly framed in self-interested terms when he noted in "Demons" that Earth needed alliances with other worlds to survive. That policy would absolutely not have been possible had Earth already developed any sort of interstellar reputation -- it was only
possible because they were the new kids on the block.
You're also forgetting that during most of the 22nd Century, the Vulcans were in no way pacifistic -- they were, if anything, an imperial power that went about installing puppet governments that would bow to Vulcan's whims in return for Vulcan military protection and resources.
And Tellarite culture is not so much based on passion
as it is on the idea that truth and good decision-making can only be found as a result of rigorous argumentation. Passion is a part of it, but passion is a part of the rest of them, too.
-Tholians: Paranoid, xenophobic
-Romulans: Paranoid, scheming
-Breen: Warlike, expansionistic
-Gorn: Warlike, value honor
-Tzenkethi: Warlike, not much else known
-Kinshaya: Warlike, religious, expansionistic
The Romulans aren't really all that paranoid so much as they are extreme nationalists. I'd equate them to 18th/19th Century Britain more than anything else. And, yeah, they're scheming -- but no more so than any other culture. (Well, save the Cardassians. Those are Machiavellian sons of bitches.)
There's no indication that the Breen are warlike or expansionists. You might recall from DS9 that the Dominion War represented the first time the Breen had ever had significant interaction with the outside galaxy; they hadn't been engaging in conquest and expansion like, say, the Klingons.
And we have no indication that the Tzenkethi are war-like. We know that they fought a war against the Federation, but we don't know what circumstances led to that war. For all we know, the Federation might have started it. The Tzenkethi can probably more accurately be described as being intensely anti-Federation than anything else; I'd equate them with Iran under the ayatollahs and their attitude towards the U.S., m'self.
And while it's fair to say that the Kinshaya have become warlike and expansionistic, let's bear in mind that they're also the victims of attempted genocide from the Klingons -- their homeworld was literally exterminated by them.
I see no reason to consider the Tholians unduly paranoid. They were paranoid about the UFP and Klingons moving into the Taurus Reach -- and they were right
, because movement into the Reach woke the Shedai and led to Federation agents committing any number of crimes. And much as we might see Ambassador Tezrene as being paranoid in her reaction to Bacco, if you look at it from her
point of view, she's not wrong: The Federation really did
rob the Tholian Assembly of a powerful fleet they could have used to defend themselves, and did so immediately before a genocidal Borg invasion. That's a pretty damn aggressive thing to do, especially since Bacco only did it as protection against predicted
Tholian aggression, not because the Tholians had actually
done anything. It's not unreasonable for the Tholians to feel like the Federation endangered their very existence; really, it might not even be unreasonable for them to declare war on the Federation in retaliation. That they reacted as calmly as they did is something of a minor miracle.
There is absolutely no evidence whatsoever that the Gorn are generally warlike. The Gorn have attacked the Federation exactly twice -- once when a Federation colony was established on a world they had claimed and they believed themselves in danger of Federation aggression, and once when a pro-expansionist faction led a coup and overthrew their government. Both times they were placated with diplomacy and then good relations were restored.
I was always under the impression that the main reason that the UFP was eventually formed was because the humans helped to balance out the other species. The Vulcans and the Andorians had been basically at war until humans stepped onto the scene. Their positive relations with both sides helped to ease the tensions. Same goes for the Andorians and the Tellarites, who were frequently antagonistic towards each other.
That was a part of it. But it's probably important to also bear in mind that those cultures had to undergo some fundamental changes themselves (as did Earth). Part of the point of "Demons"/"Terra Prime," after all, was that Humanity was undergoing a fundamental cultural shift as they learned to stop being insular and to reject xenophobia and ethnocentrism. The Vulcans were undergoing a profound cultural shift with the discovery of the Kir'Shara
and rise of the Syrannites. So I think it's important that we not use language that seems to imply that Humans were the magic ingredient that made everything okay -- it's a bit self-congratulatory, after all.
The TP doesn't have one species that keesps the others from going at each other's throats when things go bad.
I don't think we know enough about the TP cultures to make that judgment. It's entirely possible, for instance, that the Gorn will assume the function of the "honest broker" -- the TP equivalent of Switzerland, so to speak.
My guess is that the Romulans are already hedging their bets so that if/when the TP falls apart, they get the biggest advantage of the group out of the whole thing.
Hardly. The Romulan Star Empire is the state that needs the Typhon Pact the most. It's the RSE whose space was devastated by the Borg, the RSE that can't feed its own people, the RSE that's been plagued by political instability for years now. And it's the RSE that's surrounded by (what they believe to be) hostile powers in the form of the Federation, Klingon Empire, and Imperial Romulan State. If the Pact fails, the RSE economy goes into shambles and Tal'Aura will probably find herself assassinated. They need the Pact to stabilize their economy and begin rebuilding their military might; they're going to be the ones trying desperately to make it work more than anyone else.