Sigismund still can marry Barbara Szapolyai thus gathering Szapolyai support.
Barbara/Borbála is around 9 at the time, while Sigismund is almost 40. Even with Medieval measures, that's a bit far-fetched imo.
I see that you want to save Hungary from Mohacs, but IMHO even with Sigismund taking the throne it wouldn't happen.
Well, that's just you and your pessimism
. Anyway, we're not quite there yet to discuss that in the context of the sceniario.
Sigismund was more capable than this eldest brother and he would not piss of Ottomans.
Having such a large continous empire would piss off the Ottomans nevertheless, but I get what you're saying.
For me Corvinus would have little chance to succeed. He is a bastard, and he's young and inexperieced. In addition, a fair share of Hungarian nobiliity wasn't exactly fond of Hunyadis.
He wasn't that young by this point though. And he certainly amassed a lot of experience in fighting atleast, but as you mentioned, he certainly wasn't loved by all the magnates. Still the South and a good chunk of the common nobility would side with him.
Even during Matt's reign there was a plot to dethronize him and replace with Jagiellon.
That happened quite a long time ago, and Corvinus had nothing to do with it.
Maximilan is an only serious competitor for Sigismund, but he's not too popular among lesser nobles.
That's true, but Corvinus might side with him, especially if Szapolyai sides with Sigismund like you proposed.
Hungarian diet outright banned Habsburgs from succeeding the throne in 1506.
The year is 1505, and not just by Habsburgs, but all foreigners were banned from taking the throne. In the end though, it wasn't a proper diet and had no legal binding.
Rights are dubious in the case of post-Posthoumous Hungary, Leopoldine Habsburgs have exactly zero Luxembourg blood in their veins
That doesn't matter though, since it was the Treaty of Pozsony, which assured their succession, not their relation to the Jagiellons.
Deal seems likely, Sigismund would be willing to make it in exchange of being recognized as a king of Hungary.
Alrighty.
When Sigismund inherits Poland-Lithuania the huge empire is born, but Poland and Hungary will IMHO compete for leadership in this union, and the outcome depends of many factors (approach of the monarchs, activity of Turks/Moscow, etc, etc).
That is just natural. Maybe Sigismund would take the neutral approach and rule from Prague, but I'm not sure.
And when Barbara Szapolayi dies who is exactly Sigismund going to marry? And with Louis II never born there is no husband for Mary of Austria.
Well, Bona Sforza is still an option, no?