Ιt'll be great if you could nerf both ERE and HRE a bit. They are quite OP in EMF+SWMH setup. I believe HRE is far more OP than ERE though, cause they have Pechenegs and Rum to keep them under pressure. Ι agree with
@theKing1988 ERE is more balanced. HRE is just unstoppable.
Ideally, the HRE should get some special mechanics, as the Ottonian empire [aside from when you "pull an Otto" via an 867 start, which is clearly already amusing enough to have been worth my attention in several playthroughs] should be fun for a player to actually play (even as their first ruler/pick). [ EDIT: And being OP even as an AI from the moment you press Play is not fun IMHO. ]
I'm not suggesting anything super ambitious, but perhaps we could come up with something that can start small (e.g., low on interactive events) but still make an impact.
E.g., this is a case where I might employ a small series of laws to reform in order to become the unhindered & unstoppable beast that they are at present. Starting small, this ultimately is just more hoops that the player/AI must jump through in order to stop getting a malus to a large crop of things, but it feels a lot less mechanical than that in-game once properly "immersified."
Now, while I think that the HRE *does* warrant special mechanics (the greeks have more than enough, really), it'd be cool if the same kind of solution used here could be easily adapted to larger groups of titles with similar characteristics throughout the timeline; perhaps some of those should be part of Imperial Decay in general.
So we have to go to the drawing board here, though: what are the historically plausible reasons behind the HRE having some special maluses by default? [feedback welcome, as specific as you like]