You may instead consider every magic type as a Trait. Spells could be simply Stunts of each one. Depending on how easy shall be your magic, these Stunts may or may not fill a slot. Since you are limited by the number of slots, if a Power Stunt fills a slot, it will limit their number. If not, you could limit the number using Chanelling.
If the powers have an supernatural origin like gods, demons and the like, you may instead use Divine Magic using one Allegiance for each source of power. Cantrips are the equivalant of folk's magic.