That's just what YouTuber ParipateticPandas did, and the result is surprisingly pleasant.Taking matters into his own hands, ParipateticPandas took a grinder to the rounded edges of the iPhone 7, slicing a good portion off the sides before further sanding the corners to match. The result is something more akin to the iPhone 5, with flat sides and rounded corners. The metal didn't fully cooperate with the process, as you might expect, and the marks left by the blade are very apparent, which detracts a bit from the phone's new curves.
Still, it's a subtle but noticeable change, and still feels very "iPhone." Perhaps we'll see something similar when the iPhone 7s (or iPhone 8?) inevitably arrives next year.