Set distance limit when player joins existing game

You're playing a game, you have opponents, all is "well", than a new player pops in and lands right beside you and devotes all his forces to attacking you. Sucks! When a player joins an existing game, there should be limit on how close to your capital he can choose to start. Depending on size of map/how many players, but should be a different continent? Or a geographical distance of separation?? I don't know how to begin suggesting the distance, but a player shouldn't be able to just pop in, land right next to you and start attacking.

Learn to play the game and you wont have to worry about it

Maybe put join till turn 0
And he cant join

Just take all countries near your capital and you won't have that problem. Or put join turn 0 as said before.