I do think that, with serious tweaking, the CK2 engine can simulate the classical mediterranean pretty well. Rome would most likely be modeled somewhat on the Patrician Elective system from The Republic (again, with *major* tweaking). Heck, maybe that was one of their goals with The Republic: test out how dynastic play and elective republics mesh.
There'd definitely need to be a way to simulate the fact that, for all its problems, the Roman Republic and its non-monarchial contemporaries did allow for the common people to have a legitimate voice in the government.
Just to brainstorm how the gameplay and government of the Roman Republic might look in its own game:
- The various Patrician families operate pretty similar to the Patrician families of The Republic. Rather than building tradeposts around the map, however, they can have personal estates in various territories that would function somewhat similarly. Latifundia and the like. Each family would also have a number of citizen clients bound to them for elective purposes (not represented by actual characters, just "The Julii have 2,000 clients, the Scipii have 1,500 clients, etc. etc.). The dynastic game in this case would be a struggle to gain valuable estates across the Republic/Empire, obtain as many clients as possible, and utilize both to attain magistracies for your family (in order to get more estates and clients, of course).
- The assemblies could work as such:
* The Curiate Assembly would be composed of the head of each Patrician family, with each family head getting one vote.
* The Centuriate Assembly would be composed of all the military eligible Patrician male characters (or perhaps just all veterans), organized by wealth, rather than family, with a variable number of votes being cast randomly to represent the Proletariate Centuries (the common foot soldiers, possibly just represented by the client citizens), which would vary depending on the laws passed by the Republic (hint for players: the inability of the soldiers to have a meaningful vote in this Assembly gravely undermined the Republic).
* The Tribal Assembly composed of all male Patricians, organized by family, with each family (and its clients) getting one vote (determined by the majority of the family votes)
* The Plebian Council, where all those client citizens get together and vote for their own laws, which may or may not be in the interest of the Patrician families.
Each assembly would be responsible for electing various magistrates, and which assembly elects which could change over the course of the game, providing families various ways to get to power. The Curiate assembly might start off electing the Consuls, but your family happens to have more sway in the Centuriate Assembly. So, better get to work on bestowing that power upon the Centuriate Assembly instead. The Senate, meanwhile, would be composed of any Patrician that had been elected to a magistracy (to simplify matters). Other than declaring war, I'm not certain what the best role for the Senate in-game would be.
Bummer. Almost as effective as a locked thread.