
Are you really curious what was the exact political situation... most of them are just too crazy even to suggest.
Ottomans: Extremely high war exhaustion, at war with Hungary (and Wallachia ((((and Poland))))), no truce with Venice or any other western self-proclaimed crusader countries. By the way the "not-blockading" fleet of crusaders consisted of 5 Venetian for the Dardanelles and 2 Burgundian galleys for the Bosporus, and the Venetian got the order "Peace was made, Crusade will go on, remain in place, do not attack the Ottomans"

XVII century Burgundian sources claim that Genoese ships helped the Ottomans crossing the Bosporus (possibly residents of Galata who later sold out the Byzantine too)
Hungary: Armistice in succession war ends in dec 1444(, after that comes a one-year regency council and a 10 year regency event.) Right now Croatia, Sopron and Pozsony and a northern strip of almost all province is occupied by Bohemian, Austrian and Brandenburg forces, at war with Ottomans, war exhaustion: considerable.
There's also an other scenario when you consider Ladislaus Posthomous the main character of Hungary, in that case there is low legitimacy PU on Bohemia and Hungary, with Hunyadi and Podjebrad rebelling

Karaman: vassal of Ottomans
Serbia: vassal of Ottomans at a separate war with Venetian supported lesser lords occupying southern Zeta. Denied military access to Albania and Hungary in Sep 1444.
Bosnian Kingdom: Northern Bosnia catholic at war with the Principality of Hum.
Principality of Hum: Southern Bosnia, and northern Zeta occupied at war with Bosnian Kingdom, vassalized or subsidized by the Ottomans(though they were harassed as well by Ottoman raiding parties from time to time between 1444-1448) at war with Venetian supported Zeta.
Albania: at war with Ottomans (or Venice too<- in that I'm not sure)
Wallachia: at war with Ottomans
Ottoman tactics should tribe level, and also they should have a mechanism like they raid christian provinces, loot money&manpower and this manpower should count as separate one, and from it could recruit elite soldiers, the Janissary.
Cannons should spread like institution from Bohemia, Italy and Germany embraced it already at the start of the game.
Do you think it would be playable, with a chaotic start like this?