What if Charles VI had died on his boat trip back from Spain to become emperor after the death of his brother? I don't know whether he had been elected King of the Romans prior to Joseph's death so I don't know if he was emperor yet, but it doesn't seem to make a difference.
According to the Mutual Pact of Succession Joseph's eldest daughter Maria Josepha will inherit all of the Habsburg realms, but this raises a lot of questions:
1. Who will become emperor? Leopold, Duke of Lorraine is the son of Eleonora Josefa Maria, half-sister of Leopold I, so he seems like the default candidate, but will anyone contest his election? And will Leopold just try to claim the entire Habsburg inheritance and cut out Maria Josepha?
2. Who will become king of Bohemia and Hungary? Both kingdoms had made the male line of Habsburgs hereditary monarchs, but with the male line extinct will they elect Maria Josepha, Leopold or someone else? Hungary has just had a large revolt against the Habsburgs put down but could they pick someone else to rule?
3. Will the Grand Alliance try to put Maria Amalia on the throne of Spain or not? I don't think that at this point in the war they have a chance of succeeding, but if they decide to keep fighting will the war last longer than it did IOTL where Charles would have ruled both Spain and Austria? If they don't then will the war end any sooner with the issue of the Spanish succession now dealt with?
4. What will become of Bavaria? At this point it was occupied by Austria and the Palatinate, and there were plans to divide it between them. If there is a partition now it would presumably be split between Lorraine and the Palatinate. In 1712 Maximilian II was made Duke of Luxembourg and Marquis of Namur by the Spanish. Since the Southern Netherlands are claimed by Maria Josepha instead of Leopold, I think he would be okay with giving away part of an inheritance he has no claim to while gaining more territory for himself.
5. What will happen in Italy? Leopold has claims to Mantua and Montferrat, but Montferrat was promised to Victor Amadeus II. Will Leopold try to offer Victor Amadeus additional Spanish territory, like Finale, to acquire Montferrat? Could Maximillian II be given an Italian kingdom instead of compensation in the Southern Netherlands? If he does get Sardinia, Sicily, or Naples will Victor Amadeus get a kingdom too?
6. Who will Maria Josepha and Maria Amalia be married to? Will they both be married to sons of Leopold so that the two family lines will be united? If not, then who else can they marry?
According to the Mutual Pact of Succession Joseph's eldest daughter Maria Josepha will inherit all of the Habsburg realms, but this raises a lot of questions:
1. Who will become emperor? Leopold, Duke of Lorraine is the son of Eleonora Josefa Maria, half-sister of Leopold I, so he seems like the default candidate, but will anyone contest his election? And will Leopold just try to claim the entire Habsburg inheritance and cut out Maria Josepha?
2. Who will become king of Bohemia and Hungary? Both kingdoms had made the male line of Habsburgs hereditary monarchs, but with the male line extinct will they elect Maria Josepha, Leopold or someone else? Hungary has just had a large revolt against the Habsburgs put down but could they pick someone else to rule?
3. Will the Grand Alliance try to put Maria Amalia on the throne of Spain or not? I don't think that at this point in the war they have a chance of succeeding, but if they decide to keep fighting will the war last longer than it did IOTL where Charles would have ruled both Spain and Austria? If they don't then will the war end any sooner with the issue of the Spanish succession now dealt with?
4. What will become of Bavaria? At this point it was occupied by Austria and the Palatinate, and there were plans to divide it between them. If there is a partition now it would presumably be split between Lorraine and the Palatinate. In 1712 Maximilian II was made Duke of Luxembourg and Marquis of Namur by the Spanish. Since the Southern Netherlands are claimed by Maria Josepha instead of Leopold, I think he would be okay with giving away part of an inheritance he has no claim to while gaining more territory for himself.
5. What will happen in Italy? Leopold has claims to Mantua and Montferrat, but Montferrat was promised to Victor Amadeus II. Will Leopold try to offer Victor Amadeus additional Spanish territory, like Finale, to acquire Montferrat? Could Maximillian II be given an Italian kingdom instead of compensation in the Southern Netherlands? If he does get Sardinia, Sicily, or Naples will Victor Amadeus get a kingdom too?
6. Who will Maria Josepha and Maria Amalia be married to? Will they both be married to sons of Leopold so that the two family lines will be united? If not, then who else can they marry?