You somewhat misunderstand my point, I agree that the Italian chunk of the HRE should be perennial headache and essentially a long bloody slog for cultural dominance. My point is more that with some of the changes, especially starting with all the realm laws at zero, the effect is like reducing the primary weapon of the HRE to a sharpened spork. Which in turn makes the inevitable revolts very difficult for a human to cope with and nigh impossible for the AI. My opinion is that either the cumulative 'dog-pile' effect that revolts have on vassal opinion needs to be retuned for the HRE or instead the HRE needs to start up a notch or two on the feudal levies law (but not CA) so that it actually has soldiers to fight the rebellions with.
As it stands now, the usual sequence is that one of the Italian Lord Mayors (counts) trips off the sequence and the opinion hits rapidly push the rest of the Italian mayors into revolt (Saluzzo, Monferat, Urbino, etc). That in turn pushes the Italian Feudal Dukes into revolt (Tuscany, Lombardy), and now things get interesting. Next are the Frankish Feudal Dukes in Provence, Burgundy and Switzerland, and the capstone finally comes when practically every non de-jure vassal has revolted including the most problematic one, Bohemia.
A full realm raise for the HRE at a straight 1066 start is going to be about 4000 soldiers, Tuscany, Lombardy, Bohemia, Provence, Upper Burgundy, and Carinthia can generally raise 1k-1.5k armies. So literally the HRE is winding up collectively outnumbered. Now the revolters typically won't work together, but the bigger problem becomes that there's 6-8 viable siege armies running wild all over the HRE and the HRE can't safely split into more than 2 maybe 3 (tops). The result is that even with a human at the controls some of those revolters are going to get to 100% warscore, you can stop some of them, but not all of them. The AI, of course, is simply @#$%ed and aside from the odd mayor count that they siege to 100% is going to lose everything that's not Germany proper.