Making the UN more powerful will not be in the best interest of the people of Earth. The UN is one of the most corrupt political bodies on the planet. I'm sure you'll enjoy having them decide your taxes, what you can eat and drink, when you'll go to school, what job you'll have etc all with no say whatsoever from you as obviously you don't know how to run your own life.
If you love living in dictatorships you'd love the UN...otherwise well......
If you make it more powerful it has to have its own military, its own ships, tanks, planets etc, its own bases etc. Without that it can never enforce its will. Who would allow such bases on their soil is well no one, it would be a threat to their national sovereignty.