As a general Fyxt RPG rule, players can adjust their characters when they level up. This means players can change aspects of their character on top of the normal changes that come with leveling. This helps players adjust their characters continuously. Players can easily adapt to the game they are playing or to changes their characters as they evolve. When players make changes to their characters they should be limited to one thing per level. This would include; Traits, Archetype, Style, Focus, Specialty, Skills, One Discipline.
This is to show growth and flexibility so characters do not completely change when they level. However, the GM has final say on what any player can change.
As far as Powers themselves are concerned. GM’s are encouraged to allow players to adjust and change Powers during any Full Rest if they feel they need to.
However, final say on any character is always up to your RPG groups GM.