I think at a certain point, yes, Attack Choppers and Tanks can "turn the game into a mess", but with a game like DayZ, in a real life Zombie Apocolypse, there will be tanks and choppers. Also, giving the players more choice in this game can make this game 'that' much better. Obviously it will be difficult as hell to find the parts, the gas and the actual tank itself, so in a way, it won't be filled with tanks at every corner and a chopper in every inch of the sky.