Wow! FreedomBox looks like a really cool project!
Adding a Blockstack node to FreedomBox would be amazing - it would allow users to have a trusted node for storage and name look up.
You could also use it as a blockchain-based replacement for a DynDNS service: you could register a name and update the DNS of a name like
larrysfreedombox.id to always point to the externally visible address of the FreedomBox.
Having said that, if you're concerned with making traditional servers accessible, Blockstack wouldn't alleviate the need for port forwarding.