That would be the easiest way to go, just giving a +4 bonus with one application of the power. However, some powers don't have multiple applications, like Cure or Harm for example.
I remember posting about this somewhere on the boards, but my idea is that spells have really specific purposes, require gestures & words, and have a risk of being mis-cast. There are two important feats:
You can learn, identify, and create spells. Spells are very similar to powers, having power ranks and obeying the laws of familiarity. Each spell has a Difficulty in order to cast it correctly; if ths check fails by 5 or more a mis-cast occurs. Identifying a spell requires an Intelligence or Knowledge (supernatural) check; the DC is 15 or the opposed Bluff skill of the adep casting. Creating a new spell requires a Knowledge (supernatural) check. There are no set rules for the DC of this check, but a good guideline is to use the Craft skill table; the base DC to craft the spell becomes the spell's Difficulty. Often spells require strange or paradoxical components/theorems to be created. Spells are named according to the adept who created them.
Spell Training (Supernatural)
You learn 2 new spells, either ones you study or create on your own. Alternately, you may choose just one spell and specialize in it, gaining a +3 bonus to cast the spell and to the save DC of the spell.
A sample spell...
Hide the Path
Cast DC: 15
Casting Time: 3 rounds
Saving Throw: A Survival check acts as the saving throw
Components: Speaking a riddling poem about the place, and a broom to wip tracks away
This spell conceals the way to a location with which you are familiar (see Familiarity rules). Anyone who attempts to find it adds their familiarity with the place to the DC of a Survival check to avoid getting lost. Failure indicates the place remains hidden. For example, a character very familiar with a location must make a DC 23 Survival check to find it. This may look like an obscuring mist, local markers being moved, maps being inaccurate, or guides leaving the area. When this spell is cast, the adept can exempt certain people from being affected. Once three people individually find the place this spell is canceled.
Mishaps (Narrator chooses one): The place becomes hidden even to you, or people that you exempted from the spell. Your familiarity with the locale decreases. You become easily lost wherever you go.