I don't really understand the "excess solar power"
I can do the programming, but am I deluding myself?
I would also write a multi-master protocol based on the publishing/subscribing model which will make the application coding easier. For example a node with an LCD display that showed certain data could be duplicated and many of them could be placed around the network. Need another display in the garage, just plug one in using exactly the same code as the others.
I would then add a custom bootloader to these 1284s that allows nodes to be modified/upgraded from a central point
Is there an online resource/URL that you could recommend to expand/explain these further?