"Are there any more Air/Ground logics in the electrical system?"
lol... of course.... The Ground Handling Bus needs to know when to power up
The statements made about BTB's remaining in the last state are true. If the BTB's are open, they will remain open. If they are closed, they will remain closed.
Re the annunciator power sources. I'm sure the Boeing wiring schematics have this information (PMDG and LDS sims usually model this data correctly... although there are many variations between individual real world aircraft)
Regards.
NSEU