It looks like you have a specialized version of Sponsored Magic. The best way to approach Sponsored Magic (in my opinion) is to ask What first, then ask Who. For example, when your player first gets a sponsor, ask What sort of power she wants. Hellfire is the obvious choice. Who does she get it from? Wrath. So, for as long as she does as Wrath wishes, she has Hellfire. The war ends and her obligation to Wrath (though not her debt apparently) is ended.
Wrath trades her debt to Lust. Player has no obligation to Lust, but she does have a debt. Lust can make Player's life a living hell unless Player accepts an obligation, but she can't make Player do anything until then. Apparently Player accepts some sort of obligation (maybe she's tricked or doesn't understand that she has a Choice).
What does Player get? Again, Hellfire seems the obvious choice. Who does she get it from? Lust this time. Note that Hellfire is like gasoline, it doesn't care if it's fueling a Humvee or a Cadillac. But the sponsor might. Wrath might only grant Hellfire for violent magic, while Lust may only grant Hellfire for seductive magic. This doesn't change what the sponsored magic is, it just changes how it can be used.
Alternatively, instead of granting Hellfire, you can treat the sponsored magic more like Faerie magic. In this case the What changes every time she swaps hands. I wouldn't make this a modular power, just a list of magic types. So in addition to Mortal Magic, Seelie Magic, and Unseelie magic. You also have luxuria (lechery/lust) magic, gula (gluttony) magic, avaritia (avarice/greed) magic, acedia (acedia/discouragement) magic, ira (wrath) magic, invidia (envy) magic, and superbia (pride) magic. (Use the Latin names, makes it sound more fancy).
In opposition you can have 7 archangels representing the Virtues. So now you have Castitas (Chastity) magic, Temperantia (Temperance) magic, Caritas (Charity) magic,Industria (Diligence) magic, Patientia (Patience) magic, Humanitas (Kindness) magic, and Humilitas (Humility) magic. I listed those all in order so you can see which sin would be opposed to which virtue. This would be similar to the opposition of Seelie and Unseelie magic.
Now, if you really want to run a modular sponsored magic power, which I would reserve for someone who gets passed around a lot (which would be a sign of a game between the demons), then that's fine. In this case create a Modular Magic (sponsored) ability. Run it exactly like Modular Abilities, except instead of Form Points, grant Sponsor Points, and instead of the listed abilities, use something like the following list. Adictive Saliva, Breath Weapon, Echoes of the Beast, Pact Instincts, Spider Walk, Supernatural Sense, Glamours, Greater Glamours, Cloak of Shadows, Ghost Speaker, Marked by Power, Spirit Form, Domination, Incite Emotion, Psychometry, Mimic Abilities, Refinement, Lawbreaker, Blood Drinker, Emotional Vampire, and Feeding Dependance.
A few notes on that. One, the player should make a set of powers for a sponsor before officially accepting the sponsor. This list can be added to, but not until she has all of the powers already listed (if she lists 5 powers, she needs to have all 5 until getting a 6th). Two, the GM must approve of this list. Three, if she goes back to a sponsor she's already had, she should use the same list she did before.