I am still seeking a creative partner for this idea.
A couple of variations might be for a central character to have been very young near the end of Wolfenstein's fictional WWII timeline and to have grown up in relative isolation, being trained for the war so as to learn by direct training and mentoring for covert, guerrilla resistance. For instance....
-A young woman might have been a child in the regions of New York, or Boston, when the atomic bombs were dropped on the US, and thus has spent most of her life in a complex (either a government-built one or a well-insulated, remote one) the urban US. The early part of the game, or part of the backstory, would require determining how she'd survive and escape without suffering dangerous or deadly levels of radiation.
-Of course, there are other regions not affected by atomic radiation-- the Appalachian mountains, the desert southwest, the farm belt, etc.-- that would make for a more remote setting by which someone could be raised with a 'dual-identity'-- being quietly raised to be publicly cooperative and submissive despite participating in underground rebellion activities.
-Other options-- a branch of the church could be a front for the rebellion, openly playing support of the occupying forces and new government, pacifying the people, preaching peace from the pulpit, but in the background smuggling weapons, rebels, drugs, etc. to support the rebellion.
A completely different take is available as well-- starting early in the fictional war timeline, the character might have been a part of the Nazi party and having defected via a large-scale act of rebellion. We could write this out as a starting point, then deal with trying to prove to the other rebels her loyalty... also, it would explain the character's training and familiarity with technology, methods, operations, and secret information of the enemy.
-She could have been born just before the war started, so her parents were loyal to the Reich only in a desperate attempt to protect their children... until a seemingly insignificant secret becomes known, and suddenly, they were all sentenced to the work camps...
-She may have been the accidental product of an experiment or brainwashing and training program... perhaps cloning, counter-intelligence infiltration, etc.