I have a flat roof for my 1100 sqft home which I expect to replace or recover in a couple years. I'm considering whether I should mount an outdoor gfci electrical outlet, just coming straight up like this. Besides christmas lights, what other uses might I need it for? Good idea, bad idea?
If you have any HVAC equipment mounted on the roof, you are going to be REQUIRED to have a GFCI protected receptacle next to it for service equipment. But barring that, I wouldn't do it: no need for it, waste of money, possible site for future leaks and then it will get in the way of the future re-roofing project.
A better location, avoiding roof penetrations, better weather avoidance, and re-roofing complications, would be in your soffits. I power my gutter cables from them. Run an extension cord for holiday lights or occasional power tools.