I like duchy revocation, though it's already in CK2+.
I like title destruction a whole lot. I don't plan on destroying duchies or kingdoms, but I definitely would like to gain the HRE title and destroy it.
As for Byzantine nerfs... meh. I really hope any and all nerfs have a historical basis, and aren't something insipid like cutting income or something (when the ERE was the richest state around, historically). Really, the next DLC just needs to be Byzantine: both with the true strengths of the ERE as well as its true weaknesses. There are ways to make the ERE weaker without undermining accuracy.
Just wait. People complained and complained until they got multiple empire titles coming in an official patch: they'll complain until you can have multiple caliphates too, regardless of what empire and caliphate means.