Peach Tree III

It is not like some single player game where the other faction would just wait for you to settle internal problem. 

The moment Wei empire does that, they would be besieged by those warlords in the steppes, the Yue kingdom on the north, not to mention that the other world powers might also stretch their hands behind the scene to destabilize the Lotus Order rule in Asia

The great powers all have the possibility of being overthrown. It is unlike the Three Great Powers. 

The other four world powers were crowned by Pandemonium with the approval of the Republic and the World Government

  And it is known that the legitimacy of their rule over their continent is a legitimacy that is given by Death Monarch and protected by the Article of World Distribution

That Article is carved on the Hall of Laws in the Quorum Council of the World Government and on the Senate Libraries of Laws.