I've been trying to come up with a hypothetical use case for this. I can't use this as a server without keeping an active session right? I wonder if you could get around this by sshing into itself from inside the primary session. Is that an edge case you've considered?
For this use case, why wouldn't you just instead run a VPS on AWS or some cheaper platform?
This is a feature I want to implement: an option to keep boxes running while disconnected. Maybe with something like
ssh shellbox.dev keepalive box1