I'm sorry, but I don't think you know what you're talking about. Even with the packets stripped to the bare minimum and the tick-rate set very low, 500 players with playable latency is not possible. This isn't a matter of optimisation. Even in an empty game with no other code or graphical elements it wouldn't be possible.
There is so, so, so much involved in multiplayer it's honestly amazing that any game can get 2 players working well. You folks have no idea how mind-bogglingly complicated it all is. Optimisation isn't just something you can do, either. It always requires unique and inventive solutions to optimise anything. Optimisation is arguably the most creative part of making a game and not something that should be taken for granted.