thats amazing !! it s exactly what we need for relay nodes on solar power😍.. i was planning in raspis for these but without would be amazing..
good luck and have fun!!

i will when this one succeeds, is it more efficient on battery or what is the benefit?

what means public access computer?
webserver or do they access over ssh?

ufw and fail2ban maybe?

well you can distribute the keys physically make it more difficult..

also its useful for coorporations or associations where multiple persons must confirm spending..

but for your usecase probably adding a passphrase, which you don't backup and remember very very well, could be the sweet spot..

still simple, but if someone finds the keys/backups another layer of security..

GM