To summarize the run:
- Each province added to the HRE gives 1 imperial authority by default.
- Provinces can be re-added by leaving the HRE and getting re-elected.
- Austria can abdicate HRE emperorship by converting to Orthodox
- A country can convert through rebels if the rebel religion holds the majority among all religions by development
- Re-election can be forced by annexing or vassalizing the current emperor
- Conversion can be performed quickly if a country has an even fraction of development among two or more religions. Exploiting the development of one religion will flip the majority and allow for conversion.
- The emperor can be called into wars through their allies or free cities. If neither is possible, the emperor will defend any HRE prince versus nations outside of the HRE.
- By adding enough provinces for 50 IA or more, one reform can be passed with each re-election.
A few tips:
- The HRE interface does not update instantly. Elector backing can take two months or more to sync up. This goes for re-election as well as losing emperorship. Make sure to have enough displayed votes before sending out peace deals.
- When declaring on free cities or allies of the emperor that do not require leaving the HRE, you will still need to leave before forcing re-election so that all provinces can be removed and re-added.
- Leaving the HRE will change voter backing, but since the UI does not update instantly, it's possible to send the peace deal and leave on the same day while keeping the same votes as before.
- Try to farm as much prestige as possible from peace deals. Prestige helps with re-election.
- To be absolutely safe, ally minors that border Brandenburg, Saxony, and Bavaria. The later the war the less it matters who gets elected as the fifth reform prevents HRE princes from joining a coalition against the emperor. But opinion still matters for passing reforms. If the current elector backings are undesirable, let the game run for a few months for votes to change. If a situation comes up where Savoy will get elected no matter what, the run will probably have to be abandoned.
- Sieging down forts is much more important than winning battles. Since none of the emperor wars require 100 warscore, the enemy army can be ignored unless they threaten sieges. Set subjects to siege mode.
- The Bohemia PU is required as Bohemia is an elector and potential candidate for emperor. The Hungary PU is not vital to the run.
- Be selective of which allies to call in. Save favors and call in only those who can be fed land.
Thanks to
@alexti who first notified me of the strategy and corrected my mistakes.
Final screenshots: