Useful addition: real time replay saving in live games
So when you enter a match mid-game, you will see some crazy shit because how of the game registers moves. What if the server automatically saved the input moves from the beginning, and then sent it to someone who joins mid-game? Then you would be able to correctly see what's going on. When you join, it will load what happened before you joined. You'll see a very short replay of the ~200 frames you missed, and from then on, the game can continue like it would now. I'm not into coding or programming, but I don't think this would require drastic changes to the game.