That's quite interesting, I'll be following along! If you make it OSS I'd love to contribute. I have prosumer PCB design, LoRa, and FSK firmware and driver code experience :) I spent a ton of time on power management for AVR's  and the radios too. We had pretty strict constraints and LoRa radios can pull a ton of power.  

e-ink will be interesting, simple i suppose. 

How big is the lipo?