Coincidentially, I also had started working on the 737NG subsystems on my own a few days ago. With learning Nasal as the whole purpose of it, I started writing the electrical system from scratch based on actual documentation. So far, I had implemented an accurate battery discharge model and some prototypes which would connect the different electrical bus nodes depending on batteries/generators output voltage.
Sincerely, I didn't know you guys were already working on it, so it's kinda pointless to repeat the same work. Actually, if you need a helping hand with this, please tell me - I would love to contribute to this great aircraft.