The templates are more what you would call guidelines, than actual rules.
Damn, I can't stop using that quote.
Anyway, if the character was part of the council, he was part of the council, that's not limited to a template, that's just who he is. If you want to reap some additional benefit from it, you could take "Marked by Power" and tweak it, so it doesn't mean marked by a powerful being, but the fact that he was part of the council still holds some weight around the supernatural.
As for a spellcasting power, how about this:
Lingering Magical Power [-1]: Once per scene, you may use discipline instead of another skill.
You could replace the weapon skill to throw something, you can replace the burglary skill to open a lock, you can replace the athletics skill to jump a fence. As long as you can describe it in a magical way, you can do a small time spell. Depending on what kind of thing you do, I would see how long it might take, if it is more evocation style (weapons, for example) or more thaumaturgy style (burglary).
You could also add the sponsor debt here, if you like, either by always having to take sponsor debt when using this, or maybe have one free use per session and then take sponsor debt. Depends on how often you think you might want to use this.