Unless you redefine what constitutes an angel, I don't think this is something you can really play in Dresden, let alone as a PC. Angles have basically been shown to be terrifyingly powerful.
I think it can be done with a little creativity. Below is a character I made for our DFRPG game:
TEMPLATE: Exiled Seraphim
HIGH CONCEPT: Outcast Seraphim Artist
TROUBLE: CAUGHT BETWEEN HEAVEN AND HELL
BACKGROUND
ASPECT: MY SWORD IS A PART OF ME
Invoke: The sword is a regular long sword that does normal +2 damage. Having it helps Sal control his darker impulses. Also can be invoked for intimidation and maneuvers.
Compel: It can be taken or damaged. It can also get him in trouble with authorities in the wrong situation
As a baby Sal was left on the steps of St. James Cathedral and was raised in an orphanage. Despite being a very bright and artistically gifted young man he was beset by nightmares of blood and the supernatural that left him moody and disconnected. Despite his peaceful nature he struggled with a righteous fury that threatened to overwhelm him when faced with acts of evil. While he was in high school he severely injured three young bullies and left a fourth in a coma when they tried to beat him up. He has never forgotten what can happen when he gives in to his anger. Father Atkins at the orphanage gave him a long sword and encouraged him to train with it. The sword felt completely natural in his hand as if it were a missing piece of his soul. Training with it helped Sal learn discipline so he could better control his impulses.
RISING CONFLICT
ASPECT: THE RIGHT MAN IN THE WRONG PLACE
Invoke: This aspect would work like the Spiritual Guidance effect of Guide My Hand power. Pg. 187
Compel: You are actually in the real wrong... wrong place. Or you are called to deal with something that is VERY inconvenient or comes during a bad time.
When Sal came upon a couple being attacked by a Red Court Vampire he leapt to their defense without hesitation and defeated the monster all the while screaming battle cries in ancient Aramaic. For the first time in his life he was able to truly unleash himself and that filled him with a joy that terrified him. Strangely he is always around when dangerous supernatural factions threaten Seattle. Sal works as a bartender at the Rat and the Raven in the U-district. The bar has gained a quiet reputation as a place one can go if they have problems that the mortal authorities cannot handle.
THE STORY
STORY TITLE: DANCING ON THE HEAD OF A PIN
GUEST STARRING: Zebadiah Einar
ASPECT: MORE THAN SKIN DEEP
Invoke: When viewed by the Sight or other mystical senses Sal appears very much like a normal, if especially gifted, mortal. He is sometimes discounted as a threat because he seems normal.
Compel: Supernatural creatures are drawn to him. Predators think he would make a particularly tasty meal or instinctually hate him and want to destroy him.
For years Salvador Delgado, orphan, struggling art student, bartender and defender of the innocent, has known he is different. He had no idea just how
different until he found himself battling a fallen angel. His Spirit has been bound to a mortal soul clouding his memories and he is now
mortal possessing barely a hint of his former glory. But who did he serve? Heaven or Hell? Facing the warring factions of Angels and Demons and hated by both sides for reasons he does not understand, Sal must cling to the one thing in his possession that both sides disdain: his humanity.
GUEST STAR
STORY TITLE: AN UNKIND CONSPIRACY
STARRING: Adrian Huggins
ASPECT: RIGHTEOUS WRATH
Invoke: Sal can tap into his Seraphim Heritage when faced with the supernatural providing him with the strength or insight he needs to triumph.
Compel: Sal's nature makes it difficult to walk away from confrontations. And once it comes to blows his fury is difficult to restrain.
When his friend, Adrian Huggins, becomes embroiled in a Conspiracy involving the Monoc Corporation, Sal has little choice but to test his mettle against the fabled Valkyrie and the Einherjar of Valhalla. Even with an Exiled Angel helping him how can Adrian hope to survive the machinations of the God of Lies?
GUEST STAR REDUX
STORY TITLE: RETURN OF THE JAGUAR
STARRING: Fernando Torres
ASPECT: TELL ME YOUR SORROWS, FOR I KNOW WELL OF SIN
Invoke: In social circumstances many people trust him completely and open up to him.
Compel: Mortals with the stain of guilt on their souls feel uncomfortable in his presence sometimes lashing out.
While tracking down a nest of Red Court Vampires Sal ends up facing a ferocious Were-Jaguar outside his bar. After trading blows they both realize they that they have the same goals and unite to face the bloodsuckers in their lair.
SKILLS (30+4)
Superb (+5):
Great (+4): Athletics, Weapons
Good (+3): Conviction, Endurance, Fists, Presence
Fair (+2): Alertness, Lore, Might, Rapport
Average (+1): Contacts, Discipline, Empathy, Intimidation, Scholarship, Stealth
Stunts
• PASSIONATE ARTIST. (Use Conviction for Art with +2 for Painting)
POWERS
• Inhuman Strength -2
• Inhuman Speed -2
• Inhuman Recovery -2
• Inhuman Toughness -2
• Catch Magic/Restricted +2
• Exiled -1
Essentially he was based on an optional character found in the Armageddon game from Eden Studios. Exiled is explained below:
EXILED -1.
• NOTHING TO SEE HERE. You never appear as anything other than a potent souled Mundane to any form of supernatural detection. Further, you cannot be scryed or sensed at a distance with any form of power, no matter what its source. Divinations will not reveal your presence, either in the future or the past, you are effectively invisible to powers that might locate you, even if you wished it otherwise. Anything carried on your person is protected in this manner as well, making it impossible to find you with anything other than mundane investigation and senses.
What ultimately happened to Sal is that he sacrificed his human existence (and his mortal soul which he was born with when he was exiled by Uriel) to prevent the Ascension of a malevolent spirit by becoming the focus of all the power of the Ascension Ritual. He became an Archangel and essentially "died". The only thing left of him as Sal were small pieces of his soul found in his Sword of Wrath, now carried as an item of power by a PC. He was a lot of fun to play and it was realized that while he may have Fallen when Lucifer Rebelled, that stain was removed from him by his sacrifice as a mortal. Just as Uriel hoped.