Pictures? If I see this correctly in my mind, yes, you could put in a spacer between the frame and the front derailleur hanger. Just be aware that as you move the derailleur further away from the frame, the derailleur cage will sit farther from the frame and create a larger moment arm that will put more of a bending load on the frame interface. Will this load be enough to eventually damage the frame? I doubt it, but depending on how robust the frame manufacturer made the the hanger area of the frame, it could become a potential failure point over time.