PhilThib wrote:China might be challenging to play, but you would lose quite a lot of the other interesting aspects of the game: colonization, industrrialization, technological research, even quite a few elements of the Victorian age diplomatic activity...
I would say Ottoman Empire should be a bit more 'interesting' on that respect...
At the moment though, the game
focus is still on the Great Powers
I agree that there should really be emphasis on China being modeled well. It's not easy to do as Paradox games show and by making it a potentially monolithic player (and making that playable) entity would clearly remove the historical status of generally being a punching bag. Of course, it would be nice to turn China into an industrial nation (well, lets call it turn parts of the coast into industrial regions...

) but any designer would have make sure it's one heck of a challenge, and balance it with the playability of the rest of the nations.
I think you could make similar arguments for including the Ottoman Empire, or somewhere like Sweden (you could have a very hard route to Scandinavianism, although time-frame may be a bit late for that), Brazil, or Argentina. But, I think these would best be handled by modders with the time and interest to model them well - for the main game it's totally understandable that the developers want to focus on the actual industrial powers of the time, so as that they can get the game behaving appropriately without diving into all kinds of highly specific situations and contexts. Otherwise I can see a player Brazil becoming a great power easily, almost by default, with none of those pesky real-life problems that stifled its growth.