What is the largest Bavaria could plausibly be, with a POD during or after the reign of Louis IV Holy Roman Emperor?
One that replaces Austria as the Empire southeast of Germany.
Depends what you mean by Bavaria. A wittlesbach led German monarchy centered on Munich could conceivably make the Holy Roman Pire into a unied state that survives today.
In my "The Mighty Houses have Struck out," and also in one where just the Emperor/Austrian Archduke dies but Louis XIV survives (and which name I forget), Ferdinand Maria gets Austria and then Bohemia. In my TL, I'm pretty sure I recall he gets elected to Bohemia and he gets Austria through marrying his son to he oldest of Leopold's daughters, who in that TL is the only surviving child of Leopold.
he could have gotten Milan had thigns gone right, too, then, but they were trying to divide thigns because a lot of thrones went belly-up at once. You could have Ferdinand Maria's brother, who I think was in the Church OTL, marry a Duchess of Milan and then Ferdinand Maria's heirs get that if one of them dies without issue. Not sure how easily he'd get Baden, Wurttemburg, etc., but if he absorts Bohemia and it becomes his, you've got the start of a pretty good chunk of Centeral Europe just with a 1670 POD, potentially. Before then, you can get more.
Fair enough. I'm interested in changes mostly in the high middle ages, and my thought process is centering around reversing the decay of the stem duchies into further petty states. However, it occurred to me that, because of how far afield Wittelsbach/Bavarian possessions were historically, something still larger might have been possible. I had the idea that, with cards played right, most of what was West Germany in our timeine could have ended up Bavarian, but such seemed unlikely, and I'm not committed to that idea anyway, hence the ambiguity of the OP. Beyond that I'm open-minded.You are too vague.
If you expect others to answer your question with details, then please give more specifics. Else it sounds like the AH equivalent of "do my homework for me".
*No Treaty of Pavia would be a good start.
* The alt-Ottoman (or another Balkans-based Muslim) empire conquers Austria up to Linz, Bavaria resists and unites with Bohemia and Tyrol into a strong, frontline "protector of the faithful" state. Later they acquire vast parts of the Rhineland based on the Palatinate.
* Due to different dynastical developments, the Bavarian possessions Holland-Zeeland-Friesland and Hainaut become the nuclei of a Low Countries conglomerate, with, randomly picked, Brabant-Limburg, Gelderland, Cleves-Mark and Juliers-Berg. After the begin of an alt-colonial era, the maritime power of the Bavarian possessions enables the Wittelsbachs to acquire more territorie overseas as well as inside the HRE.
Fair enough. I'm interested in changes mostly in the high middle ages, and my thought process is centering around reversing the decay of the stem duchies into further petty states. However, it occurred to me that, because of how far afield Wittelsbach/Bavarian possessions were historically, something still larger might have been possible. I had the idea that, with cards played right, most of what was West Germany in our timeine could have ended up Bavarian, but such seemed unlikely, and I'm not committed to that idea anyway, hence the ambiguity of the OP. Beyond that I'm open-minded.
So we'd have parts of Austria, southern Germany, and the areas around the Rhine all consolidated?