There are seriously no bathrooms to use? no port-a -potties or McDonalds or Starbucks available? I would never survive or I would be squatting behind a car into a cup because my bladder lasts about 1.5 hours unless I'm cold then it is less.
I always wanted to go there but I don't think I would make it/
Good luck if you go. Seems like a once in a lifetime thing.
There's a McDonald's and another fast food thing in Times Square, though I think they close early on New Year's Eve (and don't have the capacity for that kind of crowd to use their bathroom, heh), but regardless the issue is that if you leave your pen, you're not allowed back in once the pens are full.
So if you want to go to the bathroom, or go search for food, you can't get back to your spot, and as people show up hours early to claim the spots.... you see the deal. You couldn't go behind a car either, because you'd have left the pen. Once the pens get filled, they only allow people out of them, not in and out.