It would work great with some kind of whole world mod, and if it allowed the releasing of vassals... had more colonists, leaders for the nations, had a better AI for each of them....
Would be great with a mod focusing on it.
By the way, adding more nations to the scenario is really easy...
Adding even more would be a good idea though - it's still a far too passive game, even with I think 10 nations in Europe.
I'm currently working on such a Mod based upon Arabia Universalis map, with new Tech, new AI, more random events and some more enhancement.
At first I was thinking putting in it all the AU starting nation (some 295 almost !) but the game become to laggish, because of too many explorations, colonizations and wars going on, it is a too heavy burden for CPU calculation....
So I restarted from scratch adding countries in bunch of 30 up to find a good compromise between CPU usage/level of challenge.
It is meant for world-conquest game and confirmed players.
The main problem I'm facing is that AI's countries become
very passive once you (the human player) reach a large size, large income, large army.
It seems they freeze scared at death of you !
I will present it soon (a couple of weeks) in the User Modification subforum.
Best regards