I think that's probably a fair assessment of the problem.
And that kind of defeats the whole point of having the HRE in the game. It's meant to slow down the agglomeration to a crawl, it's not meant to be a blob slingshot for the Emperor or just another place full of blobbing small countries. IMO there should be no way that the Emperor can reform the HRE before the Reformation, and the earliest path to HRE nationhood should be via winning the 30yrs war.
I think the real problem is that Imperial reforms are more or less a one-way track to the super-blob. It should be possible to pass all the reforms by the end of the game, but only with a *consistently* powerful and active Emperor. Other powers should have much better options for not just halting, but reversing the reform train if the Emperor drops the ball or if a weak Emperor is elected. For example:
- The 'revoke reform' peace demand should be much cheaper.
- It should be possible HRE countries to take a formal diplomatic stance in favour of revocation of reforms. The AI is increasingly likely to do this as the reforms build up. Electors will give voting bonuses/penalties on this basis. If too many members want to revoke, a kind of coalition war can start (even after Ewiger Landfriede).
- The Emperor should be able to revoke reforms voluntarily if the current level of reform is unpopular in the Empire, and automatically if he was formally in favour of revocation at the point of being elected. (It should be a viable tactic for anti-reform candidates to try to get elected Emperor, even if they can't hope to hold onto the crown forever.)
- Every time a reform is passed, everyone who voted no should get a temporary CB to revoke.
- If a lot of reforms have been passed, the Emperor should be susceptible to rebels (Reactionary? Noble?) who want to reverse the reforms.
There are also ways in which life ought to be made harder for the Emperor. Number 1 is that the Reformation needs to hit much harder than it does at the moment, with 'Enforce Religious Unity' becoming effectively useless once there is a critical mass of heretics.