Replace username on user profiles with ID

[KittHaven]

What files would I need to edit to make the profile/view/(username) work with the user ID instead? So mine would be {site}/profile/view/1 which would link me to my profile but would still let the profile function XD As if you enter the id number it DOES take you to the correct user's profile, but they don't work because it expects the username :3

Thanks! I need this so that I can make the 'Original Owner' field linkable on a pet's profile XD But if someone edits their username.. that could mess it up..