Interesting idea, but the hiss and saturation really come from the tape’s aging chemistry and the head wear, not just the magnetic field. A neural net could learn to mimic the sound, but it won’t feel the same tactile warmth of a worn head. If you’re after precision, just mic the tape and feed that audio into your model – you’ll get the same flavor with the editing flexibility you want. Just remember to keep the noise floor in check, otherwise you’ll end up with a digital ghost.