Could they not also take the nickname of someone who is the incumbent and has a known nickname? If you change it to “I want to be known as Superman,” you could have anything you want there.
That's my concern: if you leave it that open-ended, there are.... We all take the election very seriously, but there are others who have a different reason for participating, and winning may not be their major objective. I'm just wondering, how do we...? In the extreme, you'd have a ballot with Donald Duck and all kinds of crazy things, so what's the check there?