Ability to change a users profile picture back to default.

I made a discord server for a school project. I made a discord bot that makes sure there can't be anything inappropriate. The one problem I have is profile pics. Anyone can make it whatever they want. So, like names, I suggest they can be edit profile pictures. One way to implement it in is to make it so only it can only be reset to default. Not changed. This would also prevent mods from being abusive.