I think the problem is not that they were not expansionist, but that expanding north into the nomads had nothing to gain and was impossible to hold.
It's really not about Ming was expansionist or not, but that Ming was never strong enough to expand into the north shortly after 1444. In 1449 emperor Zhu Qizhen was defeated and taken prisoner by Oirat in the major battle of Tumu, and after that Ming military went on full defensive, relying on expensive fortress system on the north. On the other hand, the resouce and manpower that Ming government can mobilize was in steady decline despite that economy was growing and population was booming. Such phenomenon is obviously beyond EU4 generic mechanics' capacity to explain, so instead of trying explaining, pdox just add a stupid 50% min autonomy limit to tell us that Ming sucks at the start but can get better in the future.
But in reality, Ming government was very efficient and expansive in its early years, but would become more and more corrupt, inefficient and inflexible in the future. I think the challenges that Ming faced can be appropriatly represented in game, and give players a way to fight them.
First, remove the min autonomy limit and give celestial empire estate setup.
Tusi estate (土司, native chieftain autonomous system) should work like the Dhimmi, it can only be given to non-confucius provinces with non-chinese culture. Tusi province should have a very high autonomous floor like 75%, but no penalty on manpower, minus unrest, and impossible to convert. Tusi would require 0% percent of development but an event would popup every time Ming conquered a not confucian nor chinese province, asking for player to choose between creating Tusi or high unrest in the province.
Shishen estate (士绅, Scholar-gentlemen, the union between bureaucrats and landowners) is the real master of imperial china so they would require a huge chunk of development. They give a normal 25% autonomy floor but remove penalty on tax base. However, multiple negative events could happen in a shishen dominated province.
1) Violent land consolidation. It's the most important issue that caused Ming to decline in real history. Powerful landowners using their bureaucratic privileges to force peasants into selling their land and become serf or refugees (so it causes unrest). Also in this process, a lot of land would be removed from the official record, thus reduced the tax base (in game it should not affect the real tax base, but a modifier on tax base). To give you an idea of the scale of tax base reduction in history: In 1391 there were 8804623.68 qing farmland on nationwide government record, in 1502 there was only 4292310.75 qing left. (<明代黄册制度>, 韦庆远, 1961) When a land consolidation event happens in a province, player should be given three choices: a) stop the shishen from acquiring lands using adm points/mandate/religious authority, thus avoid reduction in tax base, take estate loyalty loss and a provincial timed noble rebel unrest. b) do nothing and gain estate loyalty and influnence, let the tax base shrinks and get a timed peasant rebel unrest. c) try to put more tax on the now reduced tax base using adm points/mandate/religious authority, get less reduction in tax base, but a permanent peasant unrest.
2) Collaspe of Weisuo system. The weisuo (卫所) was the military personnel system in Ming dynasty, it basicly consist of fixed, hereditary soldier family called junhus（军户）, given small fraction of land to sustain themselves at peacetime. They are the prime target of land consolidation, often turned into landless serfs of officers, and borrowed out by officers to landowners as labour. In time, more and more junhus would manage to escape their obligation, and weisuo system failed completely by 1550s, seriously damaged Ming government's ability to mobilize manpower. Not sure how to represent this in game, the loss in manpower is real, not hidden (unlike hidden lands), so it shouldnt be a modifer. In reality what Ming usually does was appointing new families as junhus, so maybe player can choose to take 1 manpower loss for 1 random tax base increase (the deserted junhus would eventually settle down somewhere), or take 1 tax base/production loss instead of manpower.
3) There were the wokou raid in southeastern coast, severly affecting Ming's overseas trade, but I havent thought this through. It should happen due to lack of trade protection in the southeastern trade nodes, and the lack of trade protection should be the result of naval policy shifting after the last voyage of Zhen He. Maybe it can be made as a disaster?
And the millitary estate should exist too, but not the merchant guild - they were never an independent faction during imperial chinese history.
The faction system needs a rework, particularly the ridiculous temple faction. It should be replaced by the millitary faction, which is still quite influential before 1449 battle of Tumu, but their social profile would become lower and lower in later centuries. The bureaucrat faction should be spilt up into at least two, a conservative one and a reformative one. The reformist bureaucrat faction was best represented by Zhang Juren, imperial senior grand secretary from 1572 to 1582. He did everything he could to combat the land consolidation, bureaucratic corruption and failure of millitary system, enacted reforms on tax system and to reclaim tax-exempt land. This would become the main function of reformist faction in game, to get rid of all the debuff we get from shishen estate events.
I think it would be awesome to combine this with the new mandate system. Under conservative bureaucrats, we get mandate through events of imperial rites, grand ceremony of Confucius, and suffer from shrinking income and manpower. Under reformist leadership, we spend mandate to get rid of previous debuffs. I assume low mandate would still be very damaging to china, so player would not want either faction to stay in power forever. Actually that's exactly how Ming emperors works in history. Also the number of tributary state should be a steady source of mandate income.
I can also think of some special rebel and disaster types for china. Refugees are the most horrific rebel in Chinese history, in game refugees should be able to raise another army instantly from any provinces they captured. So players must stay focused on defeating they early before they snowballed (which is exactly what happened in the last decade of Ming). About the special disasters and confucian mechanics, if anyone is interested in these ideas above, I'll discuss them later.
