The world would probably be bankrupt if there really was world peace.
Well, world peace is hard to imagine..
Assuming this is the World peace where everyone is ALIVE, and not all dead..
It'd probably be a point where everyone has a serotonin regulator inserted at birth..
Then at that point, Everyone can be happy doing whatever they're tasked to do..
Now as to Who's to be in charge.. assuming we can aptly FEEED everyone, then it doesn't really matter..
We might as well setup a roulette achievements system.. and just spin it once every few years to tell us what GOAL we should attempt next..