So, here's the plan.
Packet radio using TNC-Pi, with dialup as backup / access for people who can't reach over rf (it's only a 10w radio)
Probably won't be a classic bbs, but possibly something you can telnet into and access mastodon.radio via command line, maybe some basic "email", possibly access specific sites over gopher?
It won't forward anything to the Internet, but I'm thinking it could proxy specific stuff.