Any victory by the regency forces in the Second Palaiogian civil war would see a shift away from the total aristocratic dominance of the Late Byzantine state as the power base of the Regents were the Urban poor, merchants, bureaucrats and the church- all segments of society that had something to gain by knocking the aristocracy down a notch and reforming the current fiscal system.
Good post, and well said.
I was watching a documentary about how the English Parliament and Magna Carta came to be, and it does seem to have been similar to that scenario in some ways. In that the system was forced to become more representative because that's where the balance of power shifted. It's a real shame the Regency didn't win in Byzantium.
Now really the wildcard is Serbia, whos intervention isn't determined. Remember that John Kantakouzenos had to personally convince the Serbian king to interphere, promising land in return. Should John K be killed or captured prior to this, its unlikely Serbia would interphere. At the same time, Bulgaria was allied to the Regents and had already gotten what they wanted. They were content to sit the war out until things got really bad, so should this civil war be wrapped up relatively quickly, then they won't interphere.
This makes me think Kantakouzenos is the man who caused the fall of the Byzantine Empire. This kind of behaviour, inviting a foreign enemy into the heartland in pursuit of a selfish interest, is exactly the behaviour that is massively detrimental to everyone in Byzantium except Kantakouzenos himself. I remember reading how his Turkish allies sent him troops, and basically they rampaged across the Byzantine heartland sacking towns and destroying villages, stealing money and raping women. They were acting nominally in his name but in reality for they were a foreign army on Byzantine land, out to smash and grab whatever they could take for themselves. It was the utter ruin of Byzantine society and death, poverty and misery for millions. What a catastrophe. It cannot be overstated. Kantakouzenos let his people down. He was a vain and petty man, a selfish man who led his people to disaster.