Damn. It's kinda hard to say how they got there...
|Only going by what I've read in manga, didn't touched novels if you are about that. I am curious if original story has more lore but not curious enough to actually read it XD
|Legal foundation is assumed because we have space feudalism in the first place.
|Theocracy is an interesting thought, but the fact they have no problem with pushing some heirs or killing others to promote their interests speaks against it.
By the way, god-kinghood is more of a fantasy concept - actual antiquity rulers only could ride their titles until they cross other big political powers. Egyptian pharaohs barely could unite Egypt with their power, primarily because other factions can easily declare they think their god is more important or any other theological reason as long as they had organised religious cult of their own.
That and humans are more pragmatic then they seem. Alexander the Great declared himself a god once, and other kings even let him play the part, as long as it didn't touch their field of interests. Touch their borders - and they had a problem with that. Crusaders declared themselves rightful owners of small provinces based on sacred visions and prophecies, but it didn't cut with larger pieces of cake.
As for North Korea - it's not even monarchy, it's people republic with highly consolidated power due to high degree of foreign pressure. If great director do at least 1/10th of what South Korean propaganda says he does his credit of trust would allow him to plow a year or two by the inertia before questions would be axed and heads would roll. We can't seriously talk about establishing cross-generational bullying organisation with this input.
So.
We gathered so far, that emperor is machiavellian political genius (but also incredibly petty) that not only basically cleared and rebuilt whole political field, but did it completely covert and without breaking into civil war and by merely victimising single noble house.
If you look at state of rim of the Empire, your suggestion about massive bribery campaign might hold water. I wonder if we will also discover royal fingers in pirates soup.
The only thing bothering me now is that he is both progressive with establishing central power and proper rules of succession and destructive with feudal degradation and corruption. I think there were people like that in history, but interesting contradiction none the less.
I am also having fun with world building galore.