Eh, to emperor in China at 1510 thought to "keep its position as most powerful state in the world" would not occur. Idea that southern barbarian is threatening to china would not even exist.
Suggestion :
- First, agree with profxyz, You should be a Tyrant. A brutal and bloodthirsty one. Ming ideology established by its founder is simply not suitable, you need to excessive violence to break precedent established by Ming founder, factionalism and scholar class domination.
- giving greater quota to Muslim in imperial examination ? Chinese Hui is loyal to Ming, less confucian, more involve in trade, and many come from NorthWest where military concern is more near.
- invite Western missionary and scholar as guest in your palace. there will be little opposition to westerner and their toy if it just for yourself, you could study some western advance from imperial pockets and make replica of Western technology.
- tolerate scholar-gentry class dabbling in trade, many scholar already make some minor praise to trade and "free market", encouraging more of this laizzez faire scholar could reduce regulation on commerce and trade.
- at the same time you need "stronger, deeper state". Tax people more, build infrastructure, get state more in involved in lives of people. Chinese state usually led "local families" handle local matter, this no longer acceptable create deeper bureaucracy, create one or two more level below prefecture or district, appoint bureaucrats to handle more "local matter", let them stay longer in their tour of duty. Use people who graduate from provincial examination as local official in each province, create more involved provincial government. as a bonus provincial official would be less involved in capital factionalism.
- manage faction ? allow party to form ? its perhaps will be less disruptive to government to have party in the open, patronage and ideology will naturally create faction anyway, as long as it can be managed.
- Strengthen Salt Office, or another specialist groups, they would create rival to "normal bureaucracies". let them have their own separate funding, promotion, and career.
- don't allow martyrdom culture to develop, chinese official sometime willingly accept punishment and exile to show their adherence to confucian precept, tolerate minor annoyance, but when act, ruthlessly destroy friend, family and protege of dissident official. don't allow official to have supporter who praise them as martyr.
- move Capital to Nanking ? nearer the coast, more merchant, less chance of successful invasion by nomadic tribe
- strengthen power of military governor ? Like an-lu-shan this could end in disaster but more independent military governor could make more effective military machine. Set region north of Yellow River to be virtually independent, tolerate hereditary succession as long as they militarily competent. Economically Hebei and Ordos is negative anyway, they need constant subsidy of money and food from central government.
- military commanderies in southeast coast ? reducing pirate influence, encourage more trade, absorb surrendering pirates to your navy, encourage better ship to protect southern trade.
- accept hereditary rule for military commanderies in periphery region, less power to scholar faction, allow for people who understand about local problem.
- expand the eunuch armies, use eunuch as intendant/inspector, military general and bureaucrats more. this could also backfire, but you need your own powerbase.
- don't depend on silver, force people to accept fiat money, and accept them as taxes
- protect the mountain, flooding caused by new American crops is helpful to the poor but disastrous to the nation. You need some flat area outside China to invade for the poor. encourage immigration to Manchuria and SouthEast Asia.
- destroy the Imperial clan, why waste money subsidizing your second and third cousin ? anybody further than grandson of Emperor should be considered commoners.