Hm, I've gotten a little further in surprisingly little time on Aaron's possible motivation. He's a closeted homosexual man with a hebrew first name in Nazi Germany, one would think he has enough suspicion and pressure on him as it is. I'd say he fears that defecting would be the final nail in his coffin and that they'd send him to a concentration camp? Regardless of whether or not his fears would be fixed in truth, I'd say that's enough to make a man want to save his own skin. Thoughts, anyone?
Ironic because @Adriane and I were just discussing what to do with Mat, and one plot idea was to have him arrested and killed because he's homosexual (which would give Klaus and potentially Aaron a personal reason to fight against the Third Reich).
I like the idea, with one suggested modification: Aaron is gay, and a high-ranking SS official knows that he is gay, and the only thing between him and a concentration camp is his agreeing to keep doing the medical research that other doctors can't do, given their lack of experience with the magical power source.