Err... Sorry, but am I the only one who thinks this is a terrible idea?
Firstly, it'll take ages to achieve anything. Remember how well Fable 3's pause menu worked...?
And not only would it need a giant host, I think a better question is: who will host it, and why? It costs money, and what happens when the host dies? We'd be locked out of playing MTA. Same if a server is on an older version of MTA, then if we downgraded to join the old one then we'd be locked out the bloody menu screen,
And for what - so we can do the exact same things we can already do, without manually joining a server? It's not worth it, and it just makes it take longer to get to the server you want to. Instead of a nice GUI instantly, you need to wait for the game to load up and join to some random server for no point.
On top of this, who decide the rules of the lobby? Who decides what you can and cannot do in the lobby, which 1. Holds thousands of players who by default join automatically, and 2. Is needed to join any other server?
These problems are not easy. Why should one server be able to forge the rules that determine whether or not you can play MTA whatsoever? You've unknowingly implemented a global ban list.
And yes, this would need a massively powerful host. Sure, you can make some players appear invisible to others, but you still need to download information from each player. That suggestion makes things easier for the clients, more than the server itself. And even if it could help, how do you choose who is, and isn't hidden? You'd need a vastly powerful computer in your host that would perform this algorithm that needs to:
. Remember who is and isn't invisible to every player
. Somehow manage a system for player driven cars, so that if somebody invisible to you steals a car the car doesn't disappear.
. Make sure that weapons, explosives, etc don't effect any other "universes" than the one the player is in
. Always ensure friends of each player are in the same universe, meaning the server itself needs to know who has what friends
. Ensure no collision detection between invisible and visible players/cars etc
That may help a teeny tiny bit on what the server needs to upload to players, but you'd need to upgrade the machines specs so much it wouldn't be worth it, or have 20 thousand servers instead and somehow dynamically connect and disconnect players from one and another when they add new friends etc.