Although not using PJON addresses as IP addresses, PJON has a few strategies that allow a PJON bus to span a Ethernet+WiFi LAN and/or WAN. I use this in my PJON-based home automation system using clusters of SoftwareBitBang based devices (a bus on a single wire plus ground), linking these clusters together and with the master with routers using the DualUDP strategy over my LAN. PJON is great for cases like this.

It could easily cross the Internet as well but in that case I would recommend using site-to-site VPN commections for security as the PJON traffic is not encrypted (encryption is a little too heavy when running on limited devices like Arduino).

I have shared my PJON-based automation library here for those interested: https://github.com/fredilarsen/ModuleInterface

Ciao gongoiler, the 32 bits address identify a group of devices that share the same bus id, so yes, many groups of devices (that may have the same 8 bits device id) can coexist without addressing collisions.

here: https://www.pjon.org/get-bus-id.php we distribute bus ids for free, for everyone who could need it.

I have never thought about the bridging strategy you propose, yes effectively it may not be hugely complicated :) if you would like to share your idea with other users feel free to open an issue here: https://github.com/gioblu/PJON/issues