Trying out an assimilation-heavy run. Here's what I'm noticing.
First thing's first, it's roughly the 1880s right now, I started as Prussia, formed super Germany, and now have formed Central Europe. (The HRE).
I have stuck with National Supremacy throughout the game, and Freedom of Conscience is my religious law, becuase my empire is literally majority Catholic, despite the fact that the state religion is Protestant.
I have made concerted efforts to eliminate certain groups. The Sorbians of Saxony irritated me by trying to stage a revolution, so I started with them. Public Schools at tier 3, the max before compulsory primary school (which I have since implemented), is worth +37.5% assimilation. Promote national values is another +100%. You'd think this would create substantial movement, but it's really rather slow. As of now, the Sorbs are still about eight percent of the population of Saxony.
Next target: Hungarians. These pops are not fully accepted, even in the HRE. They get +40 from Euro heritage, +15 or +20 from Catholicism or Protestantism, and +10 from Homeland, usually. This puts them squarely in category four. Still, the slow pace of assimilation hurts me. Even with education increased to five and national values promoted, we generally lose less than a thousand Hungarians per month. With many million Hungarians in super Germany, not a lot of hope for a massive shift.
Now, to Africa. Africa is a little bit wonky. In order for pops to assimilate, they need to A. Be at acceptance level two or higher; (which can only happen if they are not Animist or Muslim, so long as I have Freedom of Conscience enacted), and B. There must be some sort of European cultural community present for them to assimilate into. Hmmm. This is problematic. Because Africa is economically underdeveloped from my awful machinations and a lack of qualifications, it has low migration attraction. Low migration attraction means few Europeans. Few Europeans means... no assimilation. On top of that, public schooling will not penetrate here unless I fully integrate the states. That's a pretty major assimilation boost off the table.
I'm beginning to think that I should have just attempted to play for Multiculturalism, rather than giving myself this challenge. Assimilation kinda sucks. The benefit I was hoping to harness is that under discriminatory laws, accepted pops do have substantially higher wages. Will report back on how high I can get standards of living, for pops who are accepted.