Since there hasn't been announced static defense weapons for arma 3 I have a suggestion that goes well with Arma 3 era:
The IMS (Intelligent Munition Systems)
The video explains better:
http://www.youtube.com/watch?v=Lr-EH8cDdd0
The module could be smaller so it can be transported by one player (or not). It could be mountable like mortars and transported by two players.
So basically the box would be placed at a strategic location and if a tank enters the range it would be hit in it's most vulnerable part: the top.
This is just a fancier replacement of AT mines. Though bigger area of action