I think if they can log out on the outskirts of the a city that is completely fine but it sucks when you check everywhere and someone logs in and he is already in the city and you get killed because he got in not from any entrance and without making any noise.
((PS: I understand that players crashed may put a hole in this idea but dont worry, another way can be if a player logs out in a city he is moved in a straight line to the circumference of the radius away from the centre when he logs back in ))
would love to hear what you think of this idea, I think it'll enhance the game so much.