Right, that's the idea. As far as receiving messages, that's not an issue in relation to keeping private keys safe. What I had in mind above was only for posting cryptocurrency transactions to an online blockchain, not for 2-way secure communication.
Personally if I had to communicate online with someone securely, I'd either use Signal, or send innocuously labeled ZIP files with a password shared with the recipient offline, or have us both sign up for an online game and send private messages within it, depending on circumstances. I'm sure there are better techniques than these, but they are probably "good enough" for all but the most intense scenarios.
“Personally if I had to communicate online with someone securely, I’d either use Signal”
To me you’re not completely secure if you use the internet at all.
How about shortwave radio? You don’t know where the receiver is and the transmitter can be in a vehicle transmitting from lots of different places.