What would you do if you had the power to do anything?
Rule the world, change creation, make a new world, anything you can imagine ...
I would go back in time, and tell my wife how much I loved her, more often. I would do some of the things she did for me - little notes of encouragement, love and affirmation. It's so easy to take people for granted, and then when they are gone, there is nothing you can do. In a way I am doing that already, but it's not with her or for her, it's because of her.
I suppose there are loftier goals, such as eliminating war, poverty, sickness. I don't accept these as how things should be - but more a consequence of certain things, including, to some extent, the free will of individuals. To eliminate them would mean to eliminate choice. Without choice, and will, there is no true virtue.
I can't think of anything else, because I don't generally engage in wishful type thinking.