Albrecht VI: Albrecht VI the Squanderer, younger brother of Friedrich V, was a constant pain in the other's back and became his greatest enemy (except Mathias Corvinus perhaps). Having received some holdings in Styria, Carinthia and Carniola in 1437, he constantly demanded more concessions from Friedrich V in order to gain power and especially the money he needed to cover his debts. When Austria and Tyrol were in need of a regent in 1439, he tried to be chosen over Friedrich - against Hapsburg family law -, but eventually failed after having conducted more or less open civil war in Austria against Friedrich and allying with Friedrich's opponents. Friedrich managed to rid himself of Albrecht for a while by a treaty signed with Sigmund of Tyrol and Albrecht in 1446, according to which Sigmund ceded the Vorlande to Albrecht in exchange for finally being released from the tutelage of Friedrich and being allowed to rule Tyrol independently, and Albrecht agreed to give up his possessions in Styria.
In the following years, Albrecht was busy governing the Vorlande - where he was in fact quite a successful ruler and e.g. founded the university of Freiburg - and (unsuccessfully) fighting the Swiss. He reassumed his position of Friedrich's rival in Austria however when Ladislaus Postumus died in 1457. Friedrich had to agree to letting Albrecht have Upper Austria. Albrecht was keen on getting all of Austria, though, and after a very intense war with Friedrich where he decisively defeated him got it in 1462. Only his premature death in 1463 (quite probably poisoned by agents of his brother) prevented him from entirely breaking his brother's power and allowed the latter to unify all of Austria with Styria.
There are three things that I would like to do here:
1. Allow Tyrol and Austria to choose between Friedrich and Albrecht as regents in 1439. Chosing Albrecht avoids a vassalisation to Styria, but results in worse DPs and a worse monarch during the regency
2. Have Tyrol release Baden by an event in 1446. It should be able to avoid this by a B choice where it asks the Swiss for protection against the Styrian brothers (there were in fact some negotiations between the Tyrolean estates and Swiss emissaries before Sigmund was talked into accepting the treaty). This Baden - ruled by Albrecht VI - would be involved in the events for the succession of Ladislaus. Baden would be returned to Tyrol upon Albrecht's death in 1463.
3. Redesign the events for the succession of Ladislaus, or in fact create events that somewhat ressemble history (right now, Austria just inherits Styria in 1463). As for results, in 1457 (at least with the historical choices) Upper Austria (on the vanilla map the Salzburg province) should go to Albrecht - i.e. to Baden if it exists, otherwise to an independent Austria reduced to that province and ruled by Albrecht, and Lower Austria (currently the Austria province) to Friedrich. In 1462, Lower Austria should pass to Albrecht, and in 1463, the territories of Albrecht and Friedrich should be unified. The question is how all this should be handled event-wise. My proposal would be the following
Event 1, 1457, for Austria
Trigger: Baden and Styria exist, Austria is AI
Salzburg is ceded to Baden, an event that has Styria inherit Austria and gives it cores on Austria and Salzburg is triggered, Baden gets an event that tells it what happened and gives it cores on Austria and Salzburg
Event 2, 1457, for Austria
Trigger: Baden and Styria exist, Austria is human
choice A: Support Friedrich
Salzburg is ceded to Baden, Baden gets an event that tells it what happened and gives it cores on Austria and Salzburg, Austria inherits Styria, gets slavonic culture and moves its capital to Styria (Graz, Friedrich's residence)
choice B: Support Albrecht
Austria is ceded to Styria, Austria inherits Baden
Event 3, 1457, for Austria
Trigger: Baden doesn't exist, Styria exists
Austria is ceded to Styria, Styria gets cores on Austria and Salzburg
Event 4, 1457, for Austria
Trigger: Styria doesn't exist, Baden exists
Salzburg is ceded to Baden, Austria gets slavonic culture
Event 5, 1457, for Austria:
Trigger: neither Styria nor Baden exists
Austria just gets a stabhit, some revoltrisk that lasts until 1463 and slavonic culture
Event 6, 1463, for Styria
Trigger: event 1 or 3 has happened, Austria or Baden still exist
Styria inherits Baden and Austria and turns into Austria
Event 7, 1463, for Austria
Trigger: either event 2 has happened and Austria chose option A or event 4 has happened; Baden still exists
Austria inherits Baden
Event 8, 1463, for Austria
Trigger: event 2 has happened, Austria chose option B, Styria still exists
Austria inherits Styria, gets slavonic culture and moves its capital to Styria
By setting up the sequence that way, we'd allow a player to start as Austria or Styria - with all the different strategic possibilites this implies in the first decades of the game - and end up as Friedrich V's Austria in 1463. The drawback of this is of course the need for a tag switch, but since the Albertine Hapsburg branch that ruled Austria in 1419 in fact died out and the Styrian branch was the one that ended up in possession of everything, Styria definitely deserves to be the country that survives unless Austria is human-controlled.
Another question regarding the sequence is of course whether and how we want to represent the war between Albrecht and Friedrich. We could encourage such a conflict with events and AI settings, do nothing about it being aware that it still might happen sometimes due to the cores they get on each other or actively discourage it. The last option would prevent them from entirely destroying each other and becoming easy prey for their neighbours; I'd propose testing the sequence a bit to see if that would be required, or if we can have the historical conflict and they will in most games (due to the importance of Austria, I'd want a percentage above at least 80) end up unified and become a solid power nonetheless.