If you decide to make a canon character, there are two rules for them:
1. You must make them as they are in the anime or manga. You cannot start making new abilities for them. Otherwise, they aren't canon. If you would like to change that stuff around, you're better off making a custom character. The only exception to this is if the character barely had any part in the anime or show. Then, you can change their abilities.
2. Canon characters should not be created until the character's abilities are fully known and understood in either the manga or anime. If the character's abilities aren't known yet, they cannot be created. Too many people are making up their own abilities for characters that turn out to be completely wrong.
Admins and mods must make sure they keep an eye out for this and do not approve canons that violate these rules. Therefore, all admins and mods should be keeping up with what's happening in the anime and manga at all times.