Panel and control system design is a complex subject ! There are many examples on this forum, I think you need to do some exploration of previous threads. One thing I will comment on is your mention of auto stop/start. For this facility you will need a starter motor and load sensing. The original Lister SOM's , Start-O-Matics, had an alternator which was also a starter motor, all contolled by the electro-mechanical SOM system. As soon as a load of more than 100 watts was applied the set started automatically. Whilst running it charge the starter battery. When the load was removed the set shut down after a pre-set delay.