It's both a Gamewish and a modding suggestion, if someone likes to make that.

The Time between 1700-1890 covers huge ammounts of interessting Warfare, some examples:

7-Years War: Prussia and Austria compete for Silesia
The French Revolution: The Republic is formed
War of Independence: The USA are founded
Napoleonic Wars: Bonaparte takes on the World
The Opium War: Britain captures Hong Kong
Deutsch-Deutscher War: Prussia and Austria (again)
American Civil War: USA vs CSA
Franco-prussian War: Bismarck founds the german Empire

Some Ideas...

Nations that gain Independancy should appear like the golden Horde did in Medieval, supposed as an historical event creating a new Faction with some Text to explain where it came from. The same System can be used for the USA to seperate from Britain, the CSA to seperate from the USA, Brasil to gain Independancy from Portugal, or the 1848 Revolution in Germany...

To simulate the American Civil War CSA simply appears in the South as a new Faction, the USA are forced to re-capture them by Glorygoals.

However the "Senatemissions" of the romans in RTW can be best transformed into "Parilamentmissions". If you decide for a Parilament it will force you to certain Missions or you decide for direct Dictatorship by the King and what you want... :) The Constitution should be changeable by Options, so you can be an absoltue Monarchy, parilamentaric Monarchy or a Republic by your coice.

The diffrences between the three Gouvermentalforms?

Absolute Monarchy - You rule by direct Dictatorship like in all TW-Games. You can become a parilamentaric Monarchy without a problem.

Parilamentaric Monarchy - You'll get Missions form the Parilament, if you fail or ignore the Missions the Loyality in the Provinces is lowered. You can always change to Absolute Monarchy again by closeing the Parilament.

Republic - You must by force do the Missions or you lose the Game unless you are de-elected. In Exchange all your Provinces have a loyality and economy-bonus, aswell as a morale bonus for your Troops if you are a Republic. Changeing the Gouvermentalform back to Monarchy causes a Civilwar, changeing from Monarchy to Repubilc awesome.