So you are proposing to the companies that they give up their hold on a country to let it become a democracy which will then proceed to make them into a glorified international company? They gain what from this exactly? The answer is nothing, they lose more than they gain, they simply wont have it, its terrible business.
So now you've admitted there are more Slavs than Germans. See? You cant call it a Germanic union, then try to make a democracy when the majority of the lance aren't Germanic. They wont have that, even with what little German blood they have (Since you have mentioned there was rape involved, this has become even worse xD). Sure, you'll be secure as they will get no where because they will be squabbling, but even if you managed to avoid violence at the start it could happen as a result of them growing tired with the results. Oh, and these could end up fighting each other. African countries have civil wars because of old tribal issues that wouldn't have became huge problems of they hadn't been grouped together into a country. Even democratic appeasal doesn't always worm, not after you have denied it them for so long, you could end up with them democratically demanding independence from you, and unafraid to use violence to force you to acknowledge it
Also, you are still forcing an emperor on a country which doesn't have one. The UK was formed by Scotland and England (Wales was considered to be part of England) as a constitutional monarchy politically after the two already had the same monarch. Uniting the two was only doable because they already had the same monarch, and even then there was trouble! (Not to mention, it wasnt just a standard union, oh no, it was a bailout fund for the bakrupt Scotland... And still there was trouble) In this case, you are still forcing a monarchy on people, to think they will accept it just because you smile and say they can have a parliament too is laughable. You have a monarch who is more powerful than the parliament, presumably, in which case they wont accept it. Even if he was just a figure head they might not accept it then. More fighting. Now you are changing both systems instead of forcing on on another, making it even worse
Also, I would like to point out an issue with giving one country a majority seats... The other gets pissed. Google "Scottish independence" or "Welsh independence" or Catalonian independence or anything else related to this modern independence issues and look at the reasons. You'll notice one popping up a lot: Underrepresentation.
For comparison, Scotland has about 1/10 the population of England but head to head actually have more seats, but as they have less on total they dislike it. This is a problem you will get in unequal representation, even if it is justified logically.
Its up to Gowia in the end, but tbh I think there will be a lot more trouble than you are anticipating, you seem to be going with a "We'll unify, become powerful, it'll all go fine and there will be no important or major problems because almost everyone will cooperate" and that's an idealist and almost fairy tale approach that I think will result in you not having prepared properly for the problems and will result in your union failing (And even if you were lucky enough to succeed, you will need to be lucky to hold it together while all the problems die down (Some never will) and you both coming out weaker than before, which is bad for me >:(