Wow, so I wrote a really long response yesterday that wouldn't post when the board seemed to go down for a while, and now is gone. Awesome.
There've been some really great responses to this thread so far. I think one topic that hasn't been addressed in depth so far, and the one that probably needs to be, is the issue of ancient Vulcans.
When I think ancient Vulcans, I think of our own ancient Egyptians here, from the deserty climate to the giant statues to the colorful costumes and even the dog facemasks from "Amok Time." The ancient Vulcans even seem to possess command of ancient mystical knowledge unknown to theire later descendants, much as many believe the Egyptians did. I think that the Romulans, probably, are more of a direct indication of the personality of these ancient Vulcans than the modern Vulcans are. I imagine that ancient Vulcans had an Emperor/Emperess. We know that modern Romulans have a fairly stratified society - we've seen that aristocrats/soldiers seem to occupy a highest caste, with a "working class" now seen in Nero and his fellow miners, and slaves seen in the Remans. I'd suggest that perhaps ancient Vulcan society followed a similar stratification, only withour Reman slaves. Perhaps this is where the ridged foreheads come into play, and those are seen as an "inferior race?"
We know, from "Return to Tomorrow" that Vulcan was visited (and possibly colonized) by Sargon's people some 200,000 to 100,000 years ago. Given apparent similarities between Sargon's more evolved state (able to exist as a disembodied consciousness within a "container") and what we've seen Spock, at least, capable of, I'd suggest that the Vulcanoids are definitely a more primitive version of Sargon's people. We know that there are "proto-Vulcans" even in the 24th century (the Mintakans) and there were other offshoots such as the Debrune that are said to have died out. (If memory serves, the Debrune were said to be a Romulan off-shoot, though?) In any case, we have Vulcans, and we have proto-Vulcans living on several planets between Vulcan and Romulus. I see two possibilities here: either many or all of these are results of colonizations by Sargon's people, and took place in antiquity long before the Time of Awakening, or these colonizations took place around the same time as the Time of Awakening and may have had something to do with the Romulan exodus.
I'm undecided on when these other proto-Vulcans left Vulcan (or if they were simply colonists of Sargon's original people) but I'm inclined to think in either case, based on what we now know from "Enterprise," that the Romulans left around the Time of Awakening. This both accounts for the Vulcans' apparent recollection of "those who marched under raptor's wings" and the Romulans' infiltration of Vulcan and designs on reconquering it in the 2150s. We know that the teachings of Surak offered the Vulcans a type of salvation from their warring ways (I believe that it was stated that at one point 90% of the planet was at war with itself) and I can't help but see parallels between the Roman Empire and Christianity. I imagine the Surakians (Surakites?) slowly infiltrating and spreading throughout the Vulcan leadership, until Vulcan leaders were "forced" to accept the teachings of Surak much as what happened in the Roman Empire with Christianity.
That leads me to think that the Romulans, marching under raptor's wings and all, must have subscribed to a somewhat opposite "theology" and offered a different type of salvation from the constant warring or from Surak's teachings. In "The Making of Star Trek" it's suggested that the Romulans substitute the logical, non-emotional approach of Vulcans with a "warrior stoic," which makes me think of a bushido-type code. Perhaps the future Romulans were primarily military/aristocracy who adhered to this code and opposed the loss in power that the teachings of Surak caused? Perhaps there was a civil war for control of the planet, that solidified that "warring 90%" into two factions, with the followers of Surak emerging as the victors. I imagine here that the victors offered the "rebels" the chance to redeem themselves and adhere to the teachings of Surak, but the "dishonored" rebels, still following their honor code, chose instead to go into exile, and left in either sleeper ships or very primitive FTL ships. (Given ENT's depiction of Vulcan warp drive, I might be inclined to believe the latter.)
In any case, I'm inclined to think that whatever interstellar colonization or empire may have lingered from the time of Sargon's people had long collapsed into disarray by this point. Perhaps the exiled future Romulans followed some ancient knowledge of where outposts were or once were, or stumbled upon ruins and followed them, until finding Romulus, a world with a sister planet, Remus, very rich in minerals and other resources, but located in an otherwise resource-poor region of space, accounting for their apparent resource-poverty and need to "fight smarter."
Then, of course, is the question of the Remans. I know that some have suggested that the Remans might have been mutates of the Romulan exiles. I'd suggest another alternative: perhaps the Remans were another group of "colonists" from Sargon's people, who did indeed mutate (or were mutated purposefully) for the climate of Remus? Perhaps it was originally Sargon's people who used them to mine the planet, and, when their empire failed, the Remans "reverted" to a primitive state, allowing the new Romulans to exploit them upon their arrival? IMO, the idea of an empire of sorts of Sargon's people accounting for the various Vulcanoids resolves the Reman issue nicely without having to go into rapid mutation - 200,000 years versus 2,000.
With a base of slave-labor established, I think the original Romulan society was probably not unlike the pre-Surak Vulcan society, with the addition of the bushido-type code that allowed them to stabilize. I can easily see various nobles and warriors fighting nonetheless for power and land early on before establishing a proper unified solar system. It's possible, I think, that there may have been a sort of "Dark Age" after the colonization of Romulus, in which the Romulans lost much of any technology they brought with them to infighting before properly establishing their empire. This may explain the account regarding warp drive "turning thugs into an Empire," but I don't think this discovery happened until sometime around the 20th or 21st century. VGR's "Death Wish" notes that Quinn began a war between the Vulcans and Romulans that lasted for a century, and this might be a good place to fit this, if not sooner. I'd say no later.
Prior, I think that several nobles would have declared themselves Emperor and Emperess, and fought for control, until one finally established dominance and solidified his/her position, ultimately unifying the entire planet under Imperial control. I think that the Continuing Committee probably began as some type of advisory council to the Emperor, until gaining more and more power, and eventually, combining with the Senate to wrest most power away. The Tal Shiar, I think, probably began as a type of Royal Guard for the Emperor/Senate, especially given that it's name origin seems to share origins with the Vulcan word for tal-shaya,
referring to a type of merciful execution. The Praetor, initially, would have probably acted as a Prime Minister, until finally gaining almost full political power as the line of the Emperor muddied. I can't help but wonder if the Earth-Romulan war might have been a springboard for the Praetor and Senate wresting control away from the Imperial bloodline? In any case, sometime between the Earth-Romulan War and the events of "Balance of Terror," the Praetor must have come to power to make dialog in the latter make sense.
I think the Romulan War was fought not only to perhaps reclaim their "right" as conquerors of Vulcans, but also to access vital resources that were in space occupied by Earth and her allies. I see this war as an attempt to "set up the chess board" allowing access to resources to cement their victories in future battles. I can see this loss in the Earth-Romulan War and shift from the Emperor to the Praetor/Senate as indicative of a major cultural shift in the Empire, away from the bushido-type code into more of a "survival mode" in which traditional values would begin to fade away in favor or pragmatism. It's possible that the Empire's defeat by Earth was a very critical event, forcing the Empire down its initial path of xenophobia and paranoia. As Sci
suggests, I can see an 18th century British model here with aristocracy holding power and inheriting membership in the senate, with the Tal Shiar gaining independent power as the influence of the Emperor waned. I'm of two minds as to whether the Empire continued to have an Emperor/Emperess at this point. Based on what Q said about mating with "the Romulan Emperess," I'm inclined to think that there did indeed continue to be a well-secluded, ceremonial Imperial throne into the 24th century.
So then we have, more or less, our "modern" Empire established. I'll have some more thoughts later on how I see the Empire evolving.