Regarding the idea of the Roman political trajectory, I think a lot of it will come down to how stable it can become, and the challenges it faces. Much of the time politics can be formed in reaction. Does the Triune system become emblematic of evil? Then maybe a Free Trade system is Bad.
Plus, we've also got a huge political continuity for the Romans to refer to. It makes as much sense for a revolutionary movement to be Neo-Republican, harking back to the times long ago when the Romans conquered the known world of its time (regardless of its actual truth).
I think realistically, with the Despotates as they have been, and the system of buffer states and allies, it slowly developing into a multi-tier Federal Absolute Monarchy isn't implausible, later becoming Constitutional as it begins to chafe.
But with the Roman xenophobia, and siege mentality, it could be that simply because an idea arises in the Latin West, it is rejected. I think it's really up in the air as to what it could be, with one exception.
We aren't going to see a Roman Anarchist Federation, not ever.