Yes, I think that this would be a good way to get a lot of countries to stand up and want to do a lot of good for the world, so that they could do something good and get a lot of money for going and doing it all then.
I think every nation should strive to act more dovish then hawkish, I don't believe the United Nations should be in the business of financially rewarding members who act dovish, I think the United Nations needs to sanction and condemn any nation that acts with unprovoked aggression as a United front.
No, the United Nations should not financially reward members who commit to acting like a peaceful foreign policy dove, because the United Nations cannot redistribute wealth. Also, it would be very political as to what a peaceful nation would be. The money would be political favors, not true incentives for peace.
Global government would be really bad because there are too many different cultures and belief systems. Ideals and morals of one country are completely opposite of others and a Global government would not be able to agree on a way to satisfy all of them. In addition, a Global government would further divide the rich and the poor. History has shown over and over this leads to revolt and society as a whole would crumble.
The concept is far too vague for this to be an effective policy on the international stage. What would be considered a peaceful country? And how long before the payments become standard practice on a yearly basis, for nothing other than those countries not officially at war? And who would pay?