Amusingly enough what I've come up with matches Das's ideas fairly well, sure most of it isn't down on paper [Russia

] but it's more or less aligned.
The Jing do collapse, it is occupied by the Mongols, but becomes a perennial dumping ground for whatever nomads want to break out of the steppes and wreck things. It rapidly de-urbanizes for the most part and evidences a steady breakdown in sedentary agriculture in the areas most prone to attack. It more or less becomes worthless, compared to the South.
Korea is an interesting problem, I was throwing around the idea of it being influenced by Japan through a possible invasion by the Kamakura Shogunate as a last attempt to regain some degree of a mandate at home. It would fail but secure a few nominal possessions of the Japanese which would steadily diffuse influence into Korea and Nipponese it.
How do the Song gain and influence in South East Asia? I reasoned that with the lack of invasion by the Mongols, Chinese vessels in the region would become far more common. What this would achieve would be the slow driving away of Malay traders from Śrīvijayan which would slowly impoverish the entrepots slowly turning them into ports dependent heavily upon Song trade. This weakening of the individual cities of the league would remove the hegomen status of Jambi and Palembang [at that time dominant] which would bring about a slow contraction and reorientation towards the straits proper and away from Southern Sumatra. This would be bought to a head by the Singhasari invasion in 1288, which would be checked by a hastily deployed Song fleet and the nucleus of an army which would eventually be primarily made up of allies. Which would more or less cement a new relationship, with the Song gaining the role of hegomen in the league's hierarchy. It would take a show of strength later in the decade to drive off the Khmer from the Malay Peninsula proper before the whole thing would more or less fall into place. The Song would gain a handful of cities as direct vassals, and eventually place their own Princely choices backed up by Song or Song trained bureaucrats. A few cities might even come to be ruled by ethnic Chinese who would increasingly become common. The whole lot would eventually come firmly into Song influence and more or less align itself completely. [Some extra butterflies in this whole scenario which I haven't elaborated on, it doesn't exactly go the Song's way a 100%].
The Đai Việt are also in some serious trouble, but I won't elaborate on that atm.
I'm currently up to Pagan, the Khmer, the Kingdom of Dali, I don't know about the Philippines all of which should be done tonight [expecting the Philippines which are a mess] till 1390.
Tomorrow will begin the harrowing process of handling India. Without the Mongol impetus of conquering the pleasant areas around India I don't see as many Turk fleeing them entering India. Which might spare the various native princes abit of grief, I wouldn't go so far as to say the Second Battle of Tarain will be different, but the after effects will be far lessened, at least in terms of the Muslim forces holding territory since they won't have any of the displaced Turks to play with. You’re still likely to see large tracts of the East fall, but not as far as OTL with a chance of it being blunted. Still working on the specifics of that. Sultan Raziya is kind of awesome will be doing more reading on her
Now onto addressing comments:
Actually, greater maritime trade=earlier Black Death going by a slightly different path. Italy is going to suffer.
Not the intent of this alt-hist, I would guess that the voyages in the region might be sufficient that the kill period of the Black Death will trigger, there would have been active trade and it doesn't appear to have spread that way

. But it's not the intention of this alt hist.
As a sidenote, I would have to say that the Black Death was more of a catalyst than anything else.
The Church will suffer, it already was heaving under the weight of its own sins [Dante

] I’m still interested in the possible specifics so please throw them at me, but I’ll work on those later.
You are seriously overestimating the Song Dynasty, and China's capacity for colonial and commercial expansion in general.
Covered above. The Indian entry will be sometime later, and not necessarily by the “Song” proper
Agreed, but the region will still survive as an irrigated state, which is important for later. It will also be overrun, just a touch later. This will have interesting effects for India proper and Iran later. Iran is going to be interesting to say the least, and will be rather super. Shiraz will have significant Chinese visitations, but there will others who will be equally important. It will encompass Iran, bits of Central Asia, might have a presence in India/Afghanistan and thereabouts, but will be rather constrained elsewhere.
As to Asia Minor and the Levent I have a vague idea of what’s going to happen there but I’m open to suggestions. East Africa will be amusing.
Egypt is going to be interesting, but you should not rule out another wack at the place by the Crusaders. Egypt will have issues in the middle east, by necessity of the writer and future mod
I suspect that the New World would be discovered much later than in OTL if maritime trade in the Indian Ocean prospers, though a lot depends on how the Middle East works out. Perhaps Egypto-Persian resistance to Italian infiltration of the Indian Ocean might cause an earlier attempt to literally get around this problem, though (but it won't be much good for this if they just go around Africa).
It will be discovered much later, and I’m not sure about who is going to discover it… but someone will. I see it more than likely by accident trying to shoot out to sea to catch the winds down the coast of Africa, and overshooting into Brazil.
The America’s civilizations will probably be aided by, 1) a generally weaker technologically wise Europe, 2) some delay in their discovery, 3) a less lucky Europe

they will still fall but not as hard or as quick
First of all, the Byzantines were in agony and I am not going to be convinced otherwise.
Eastern Europe overload… currently processing
Waffle on economic effects
Masada knows them, Europe will suffer
Symphony spoiling the party
Noted and ignored for artistic license, and the knowledge of only a few years ago

Suffice to say a weaker plague will be likely, heck inevitable…
