Oh OK I see, I understand better now.
You could also try to setup something like a NAT after your firewall, so you could still use the different IP addresses (though I’m not a network specialist so I’m not sure how feasible this might be).
The solution you propose (changing ports for websocket communication with rosbridge_suite) is also a nice one, however note that for now, NiryoOneStudio only works with port 9090 by default. We may add the possibility to set a custom port in a next software update. In fact, I’ll add that to our feature backlog.