Double Post, so not extra stat:
PS: I am not kidding about the VPNs either. Make your server double as a VPN server, host a webpage, make sure locals know about it, etc
Sure beats having cheaters and strangers if you host on a private 'WAN' as such, as every single player is known by the admin, with their own username & password.
To work around the invisible server issue, just host a 0 player server outside of the VPN, with just the web address of how to register as a player of that server.
(Sure its more work for admins, it is only optional, and does add some lag, but it stops ALL CHEATERS, and any assholes get banned by ID, and also have no way to authenticate to the server)
This may sound really complex, but in fact it is only a 90 minute job, and well worth it, even with the additional lag / overheads of a VPN.
It can (to a degree) also ensure the player is not uploading or downloading anything (to cheat or otherwise) thus affecting their ping, and everyone elses 'perception' of that player, since once they join the VPN, unless they know how to edit their routing tables, they will lose internet access, and gain VPN only access.
Its also good, as 'My Network Places' shows the shares on the server when they authenticate, and you can bandwidth control their usage (or host an FTP as normal, so they can use the Internet while downloading addons)
Also to the above, we also need a Server Addon manager tool, that helps players remove old addons, setup (multiple) addon folders per server, etc, etc
I am sure these 2 last posts will spawn HEAPS of FANTASTIC ideas