In my opinion Ming should have different way of Westernization - I mean, this country was so advanced in 1444 that it seems stupid that it needs to find some random poor European colony and settle next to it to achieve the technological levels of these dirty soldiers and diseased colonists being superior by... 16th century...
I mean, okay, this concept of Westernization fits American/Subsaharan nations, maybe also states from other areas, but it doesn't really fit Ming which had so powerful intellectual legacy that it could be on par with Europe if it 'just' went through 'some' reforms (yeah I guess it would be long and hard way).
IMHO Ming should have special mechanics or special Dynamic Historical Events resembling structual reforms slowly leading it to losing tech penalty. If I remember properly, there is a mod (Pax Sinica?) which does that: Ming has 10 hard - to - achieve decisions and getting one decreses penalty by 6% to the point of 0% penalty after all of them.
Other than that, one thing which is stupid as hell: there should be some way for non - Ming Han nation to become Celestial Empire, you know what I am talking about, just like it happened with other past dynasties (Tan -> Song -> Ming etc). I am not sure how it works for Qing but I am sure that there should be some way for Shun/Xi/Zhou/Yi/Miao to destroy Ming/reunite China and become Celestial Empire.
Oh, and by the way:
- An option to create Yuan would be amazing - if non - Manchu horde managed to conquer China
- This would be of course ahistorical but I think it would be also cool if Dai Viet/Korea/Japan could do similar stuff as Mongols/Manchu historically did: conquer China and create new dynasty with mandate of heavens restored.