I suspect he meant gaining the positive side of Lawbreaker; gaining a +1 or +2 to spellcasting when breaking the law again.
It makes sense from a story point of view - you've paid for the ability through permanent debt. However, I'd be wary of using this as a way to bypass refresh limits.
Well, you can always get more sponsor debt, if you want to increase your spells, so the bonus from lawbreaker isn't really necessary. And I would not give the bonus without the power, that's what it's there for (among other things).
You might also want to consider, that some sponsors might actually require a lawbreaker, especially the darker ones. Or maybe not so much require, but a sponsor will be drawn to people close to himself, so a murderous and violent sponsor will look for people prone to murder and violence. A mental magic sponsor will look for people that like playing mindgames with people. It will be a very very rare case, where a normal, decent guy will get sponsored magic like that and use it, without being twisted around. Not necessarily in a magical way, but inflicting pain and suffering on people will leave its mark, even if it is just plain old guilt. This conflict should definitely be reflected in a character like that. And if you are in sync with your sponsor, and it is a "bad" sponsor, why not take the lawbreaker anyway, since it seems you want to play exactly that sort of character.