Some event ideas, for most of them the credit goes to posters of a Hungarian forum.
First of all, I was talking with Archduke about a mega-event for Hungary which would decide her future fate. It should trigger around the 1550s or so, and it should be about which religion Hungary would go with.
First choice would be Chatolic. It would mean the "old way", with max. Aristocracy and max Decentralization, +3 Land, -3 Innovativnes and -2 Stability.
It could also give permanent CB on Poland, as kind of a claim on the throne or something.
Second choice would be Reformed. It would cause like -5 Stability, but would place Hungary to Latin tech group. -100 on relations with Bavaria, Royal Marriage with Switzerland, +3 or 4 Centralization, -4 Aristocracy. +2 Innovativnes.
Minor event ideas:
1432: Expedition to Magna Hungaria. Historically, in the 1200s a Hungarian cleric found Magyars in Asia, descendants of those who didn't go with the rest of the tribes toward the West. The second time he went to invite them he could not find them, as the Mongols ran over the region.
This event would be about finding the remnants of them and bringing them home. 1st choice: -300 gold, +5000 population to Ruthenia, with religion remaining Orthodox. 2nd choice: -1 Innovativnes.
1504: Fugger-Thurzo mining monopoly 1st choice: accept this, +500 gold, +1 Mercantilism, +1 Serfdom, +2% inflation, revolt risk up by 1 for 24 months in a couple of provinces (will provide later. 2nd choice: reject this, -1 Serfdom, -1 Mercantilism, -1 Centralisation.
1514 Werboczy Tripartitum: +2 aristocracy, +2 serfdom, +1 centralisation, +2 land.
And a possible diplomatic agreement with Byzantium would be needed. It could give Hungarian CB shields on Moldva and Bujak, with Byzantium receiving one on Bosnia or something.
In case of Hungary being Reformed and controlling a Black Sea port after 1600, a "the Black Sea is ours!" event could trigger, giving a CB shields on Crimea.