Well lets start with a few thing:
1. I love how this mod has developed over the ages, and it still has much to do.
2. Meritocracy (the concept of choosing things based on merit instead of willy nilly) is really great in this game, but the super slow 5/year increase means that i have to make sure it goes down (never) to even attempt 100 merit by 1809.
3. Your Current Governance is based of both Rule of Law and Meritocracy as far as ive seen, which all in all isn't bad. But you got rid of Beurocracy size which was the main way of increasing current governance into the high (900) values so you can run an Empire.
4. Required Governance is based off of a couple of things: a. A states (or provinces) autonomy. b. Who rules the territory (you, church, citizens, nobility) and c. If nobility then serfdom comes into big play here
5. Now current governance as is is way way to small due to the fact that any changes made to rulership of territory, or serfdom is literally a shot in the foot due to corruption countering meritocracy.
6. Insufficient Beurocracy literally kills empires, Turns out Even at 100% autonomy in all your states you still dont have a sufficient beurocracy to run a true empire (2000+ dev), and as such you literally die trying to maintain a single 20stack proper army. All the while everyone wants a massive chunk of you. (Vassals help)

My strategy so far in order to create a super ordered empire has been the following. Grab country X, slowly take noble and civilian institutions as you expand, giving you (20%-40% church ownership) and just (20%-60%) serfdom in all your states.
Try to keep privilage at around 60-70, never go curruption above 100-meritocracy, and if you have insufficient beurocracy, either
1.Sell lands to church for management, (Easy to take later with dissolution of monasteries)
2. Cell to highest bidder for civilian ownership. (Inevitable late game, do only in non-state territory first)
Always remove republican, local assembly, and civic charter institutions.
Remember the States you want to keep as states late game have the most developement and provinces, ie; most of italy, southern germany (swiss area is good), france, and england.

♥♥♥♥ is pain (hre revoke of privaliges is awesome, and you get vassals that are nothing but good), uniting the empire is a game ender - you lose all the HRE benefits you tried so hard to achieve, and you will now have 2000+ dev with insufficient beurocracy making you a dead fish country.