If the defeat of Podebrady was that simple, Matthias would have taken Bohemia proper for himself OTL.
Matthias couldn't take Bohemia, because he was too cautious with his Black Army and didn't engage in a decisive battle. The Black Army was too important for his authority to risk it. Also, his tyrant reputation made him more enemies.
John wouldn't have to face such problems
ITTL Hunyady could invade, but he'd get the same area, which Matthias got - Moravia, Slovakia and Lusatia.
(Slovakia?) Even if that's the case, Vladislaus won't be preferred over László after Podebrady's death, so Bohemia would be acquired then.
And guarantees are impossible if Laszlo Hunyady wants support of Pope - Pius II declared them null IOTL and it was the reason of Podebrady deposition.
Alright. Fair point.
Knowing Matthias's personality and what he did with his regent OTL might this be a perfect set up to a son vs father fight?
Would Matthias still have such personality TTL though? His family wasn't killed and he wasn't imprisoned in Czechia. Also there's a difference between opposing your uncle and your father, especially if he's John Hunyadi himself. John would only want to fight anyway, Matthias' hands wouldn't be tied so drastically, eventually.
also have a hard time to imagine John Hunyadi fighting a war of conquest in Bohemia instead of fighting the turks.
Even he realised, that Hungary alone is not enough against the Turks, hence did he launch no major campaigns after 1448.
He's person is also quite romanticised imo. He was also just another magnate after all.
In which case, how about going on a counter-offensive after Belgrade
Some limited actions could be taken with the help of Brankovic. Maybe a siege of Galambóc(Golubac)?
But im not sure how bad the defeat was for the Ottomans. It was a serious blow but how serious im not capable of telling.
Well there wouldn't need to worry about a large army to come imo. Maybe the Rumelian bey could be an annoyance, but that's it.