Looks like a fun project.
I am hooked on the rasp pi. They are so adaptable it is nuts.
I have built dozens of devices now with them, most have been claimed by friends and family.
I have several in use around here, and keep a few spares just in case one fails or a new idea/need arises.
I have never had one fail yet however, I had one couple nights ago, but with a hot air rework station and minor tinkering it's live too. Turned out a couple smd resistors partly dislodged from the board due to to little solder.
Are you going to have any voltage and current monitoring?
You could be able to track everything from input/output loads, batt states, calculate efficiency of the batteries etc.
Even could monitor the inverter efficiency, changes might mean pending troubles.
I would be a waste if you don't since you have the pi there already, and should have plenty of expandability and cpu cycles left.