The lack of anti-missile countermeasures in Cold War Crisis made any tank a deathtrap. I think it would add a lot to the gameplay if this feature was made available. An example of Active Protection System is the Russian ARENA, normally found on the T-90. It consists of a small radar used to detect any incoming projectiles and several protective grenades which are fired in a salvo in front of the incoming projectile (usually a missile) to either eliminate or reduce the effect of the shaped charge.
edit: pasted the wrong url to the picture. Thanks Jezz.