I like that. Would you allow a counter spell in a situation like that as the only means to remove?
Also, along the same lines (maneuvers), what about "buying zones" for maneuvers? When, if ever, would you require the caster to buy a zone for a maneuver? Maneuvers normally put an aspect on a scene but how much space would you rule that includes? When Harry froze the lake would that be a basic maneuver in your mind or would you have the character buy zones too?