Hey Scott, its my understanding that the nova lobby process works as follows:
Users clicks on novaworld, this then pulls the login page from the server, the username and password is then validated to the nova servers, which either returns ok or login failed.
After this the lobby data is downloaded from:
http://nw10.novaworld.net/jop_2.gsb
Now im not sure when a user joins a server how exactly the hand off works as the server is server that is hosting is passed the pcid (player) id as this comes from novas servers and not the players system. I suspect that when the user joins the lobby nova server passes the pcid back to the player with the lobby data, alternatively the hosting server would need to validate the players username against a pcid when they join.
You have probably already laid out how the process works, however my point is there is going to have to be a replacement system for the pcid system.
In theory this should not be amazingly hard to create, you could in theory generate a pcid for every person who is registered on your site and then tie in a login to a pcid.
Each server also has a server id, however i think this largely is just generated as a reference for the lobby system and nothing else.
I had been planning to capture at some point the jop_2.gsb file and see what was inside.
If it helps at all i do have my own lobby system that pulls the data from:
http://www.edcint.co.nz/jo/lobby/
My system was unique as it pulled the data in json format from the edcint site and then renders it in php. However all the other lobby systems display no data when nova is down, however my system was designed to freeze the existing good data until new data could be collected again. So although its the wrong (not the original) format, it does have the various bits of info, its probably not much help but i would be happy to provide the json file so you have data to play with or reference.
As well as speaking to the guys at novaworld.cc the guy who created runs the edcint.co.nz site would also probably be useful as he also knows a little about the structure of the gsb files, he was active on the novaworld2 forum recently, although sadly i cant tell you what his user name was (not that this matters at this point). However sadly the contact us part on the website is not working (disabled), however a whois shows a possible email address as : domainz at edcint.co.nz so it might also be a worth trying to make contact with him to see if he can provide anything useful to help the cause.
If you want any help testing or anything else, im happy to work with you any way thats useful to the project.