I'm enjoying this, but I'm not sure how realistic Wladyslaw giving the Byzantines all that land is, and I'm also not sure if they'd be able to recover so quickly. Still, I'm enjoying this timeline, so keep up the good work.
Władysław had a near death religious experience during his final charge at Varna. A near death experience does something to a person (I touch on this in the last update). Also, appeasing the Romans had a certain appeal to it as well.
Also, I do bring up the difficulties the Romans were having in controlling the Balkans. It's only on the word of Władysław that it even had a ghost of a chance of succeeding.
However, i do agree that if byzantines were handed all of that territory, emperor would have nominal control over the cities at best, as simply there wouldn’t be enough soldiers to enforce the control.
This is correct. There were some minor revolts and some severe banditry in the Balkans that would last for a good third of the time between 1444-1500. However, there are a few things that kept it from spiraling out of control:
1) During the campaign that led up to Varna and Varna itself the military age manpower was decimated. This wouldn't prevent rebellions, but it would help make them smaller in scope and more easily contained.
2) Also, to expand on the first point, the Ottomans also would've recruited (conscripted) men of fighting age to fight in their wars to recover from the First Interregnum that resulting from Timur never mind the fighting during that Interregnum itself. Generally speaking, the people of the Balkans were just straight up tired of war.
3) John Hunyadi, who now rules the lands between the Danube and the Haemus Mountains as a client of Constantinople, is now obligated to use his soldiers to assist Constantinople in securing the Balkans.
4) While this doesn't really impact internal stability much at all, both the word of the Pope and Władysław have guaranteed the new borders of the Roman Empire, which would definitely help with any potential external threats. This point will only grow in importance as the Romans grow more confident and assertive in the east, since they now no longer have to deal with threats in the West.
5) As for Anatolia, most of Roman rule here is nominal at best and the reason why it holds for the first decade is mostly due to the absolute shock of the Ottoman collapse. Karamanid rule over Turkish Anatolia wouldn't begin to emerge until the 1470s and what you see on the map would only be secured (in the loosest terms possible) until the 1480s. Karamanid rule would never be as strong as during the Rum or Ottoman eras. By the 1470s the Empire is capable of at least defending themselves quite well, while even raiding the Turks a couple of times.
So over all, while there are problems in both the Balkans and Anatolia, they're not so bad as to seriously threaten the Romans' ability to keep a lid on things while conditions outside the Empire are also giving them the time they need to recover in both the East and West.
As for the Updates covering the South Italian Wars, these will have a slightly different format and be less wordy. Hopefully I'll be able to put these out in only three parts.
Also, I am considering doing a map highlighting the gradual expansion of Roman Control over the Balkans and Anatolia during this period. No guarantee on it or anything, but I'm certainly contemplating it.