Space issues, right. Not to mention the inevitable flood of complaints from parents, and possibly even the Ministry of Magic. Was it even legal to transform someone into an animal with a five X rating? Not to mention in close proximity to a bunch of students.
Although if he thought about it, Nate would really have been the safest person in that situation. It wasn't as if he would attack himself. Although Erumpents did have that nasty habit of exploding...
Really, though, Nate was fine with something a little more mundane. As long as Mikey could turn him back, obviously, but Mikey wouldn't be planning anything he couldn't undo, right? "Nah, I tend to steer clear of Gnomes. The ones at my mom's house bite." A bird could be interesting, though. Nate didn't know many Quidditch players who hadn't wanted wings at one point or another.