You do make a good point, I have to admit, and even if I say that they elected her after the other contender died in their war it would still need some wide explanations on why they would elect her seeing as she had male children (even if a late husband, her brother would have died when she was 37, she was by that point long married with children, including Rudolph IV).Not gonna happen. Unless there was some sort of change way back when (I'm not even sure how early it would need to be, to be honest, probably with the Carolingians or Ottonians) a woman can't be elected empress for the simple reason that in Germany, Salic Law (the real one, not the French bastardized version of it) applied. And the electors were all male. Which makes it questionable why they would a) elect a woman over her male-line (presumably of age) uncle and b) if there was no other male candidate, why they wouldn't put themselves forward to marry her (since she seems to be single).
I think in this case I'll need to admit something doesn't work and make that in the end of the succession war instead of her getting the throne her son is elected as emperor (even if he would have been a young teen by that point) while Maria Antonia remains as the ruler of the Hapsburg monarchy (or at least the Crownlands and Hungary), although I admit if (cof cof when cof cof) I do a follow up to this line, I'll probably have the empire become at least male-preference cognatic at some point in the 19th or early 20th centuries and more centralized in the sense of the power of the smaller states waning or being willingly lost to the emperor (which was a bit of what I was trying to indicate with the changes in imperial succession)
I must admit I also didn't really think about the other components of the HRE's government. But, in light of it, heres me trying to explain after thinking about it for a bit.Not even post-Westphalia with all Ferdinand III (who was a pretty smart cookie as Habsburgs went) legal finangling of grabbing more power for the Habsburgs/emperor by playing the members of the empire off against one another (Brandenburg vs Neuburg; the Palatinate vs Bavaria; etc) did he try to pass a law that required a Habsburg to be elected. France and Sweden tried to insert a clause at Westphalia that the position couldn't be hereditary (i.e. that two members of the same family couldn't be elected in succession) but a clause to create such a succession? The electors would all have to be underage kids to allow it. France would never allow it.
And even if they did manage to make it hereditary somehow, hereditary in the German sense meant "Salic Law". The Landshut War of Succession and Bavarian War of Succession were all fought by parties who had an interest in either maintaining Salic Law. Pragmatic Sanction of OTL was more an attempt to push what was, in effect, a house law through as an imperial law. You know why Karl VI had an issue pushing it through and had to bribe people to accept it? Because the German princes were afraid that if they allowed such a law to pass that their own lands would become inheritable by the female line.
Even the Second Reich established in the 19th century was a boys' club - had Wilhelm II had seven daughters instead of sons, and his son had died without issue? None of those girls could've inherited as Empress Wilhelmine. Instead, the imperial crown would've gone to his brother. Then his brother's sons. If Heinrich had no sons, then the crown would've gone to Wilhelm I's eldest brother's line.
People often think that the College of Electors was the highest body and that the Empire was an absolute monarchy, but there was both a Reichstag (imperial parliament) and a Reichshof (essentially an imperial law court) that would need to register such a law. Since you've kept all the inter-border insanity that was a pre-1800 empire, that means you have nearly 300 votes in the Reichstag that need to agree on registering a law to not only make the position hereditary (de facto) to the Habsburgs but also allow a woman to succeed/rule. And then, since you decided for still more insanity by allowing people such as Tudors/Stuarts (or whatever dynasty is ruling England) and Bourbons (you mentioned the prince de Condé having lands in the empire) to have territories such as Fulda and Condétown, they would also have a seat/vote in the Reichstag, and no doubt control a few more votes/seats. Which means that France/England are going to use their voice in the Reichstag (as France and Sweden did at Westphalia) to sow chaos and oppose the Habsburgs, since a strong empire means one that stops tearing itself apart and can take them on.
The reasoning I have behind the making of the position be de facto hereditary is/was, I admit, confusing, being based around the idea of the Hapsburgs managing to exert a larger influence over the empire due to coming out of the Thirty Years' War analogue with stronger base and through that managing to remain not only the nominal but de facto head honchos of the HRE and being capable of either convincing or forcing a large enough percentage of the empire's states to agree to their changes. About the other states exerting influence through their territories within the HRE (Britain through Fulda, Denmark through Schelswig-Holstein and France through Condé-held Strassbourg), my reasoning about them not getting involved on the changes in the law was that the Hapsburgs did it at a good moment as while France tried to sow chaos (and was the main backer of the uncle in the succession war) on the empire, both Britain and Denmark, which had influence through Fulda and Schelswig-Holstein, had close family ties to the Hapsburgs, with a British princess as Empress and Rudolph III's sister being married to the Danish king.
About the female inheritance, I never really understood why the germans didn't want women inheriting in any way shape or form (since in the end when their males ended they always were gobbled up by some other branch of the family, although short-sighted misoginy is probably the reason), but in this case I admit I may have done a large amount of mental gymnastics to make it work and it would need an impressive amount of explanation for that. The closest thing to an explanation I have is that Karl VI passed the change in the succession of the Hapsburg Monarchy (and not the empire, as he either considered it a given or didn't think about it) in a good moment and even then it was a close call on the Reichstag due to the reasons you mentioned above (reason why the uncle, which I'm going to call Ferdinand, had enough support to start a war over it later on), with the law also specifically mentioning that it would not have any correlation to the other states of the empire in the matter of their own succession (although many of her supporters would change their laws to semi-salic (or "if every single male in this family dies, then a woman can inherit") in the aftermath of the war).
Does that make sense to you? (It does to me, but...)
It does sound very snarky, but I get why you're being snarky, some things that I wrote sound extremely absurd without some explanation (or even with it)Sorry if this sounds snarky, but the empire being made any more hereditary than it was (OTL even the elector of Hannover - who under his "letters patent" creating him elector was obliged to always vote Habsburg didn't in 1741 after Karl VI died) seems implausible under the scenario you posited.