One stone? They are very desirous of nuking it - one of the uses Iran intends when they have a working nuke stock pile, missile ready warheads, and reliable delivery systems. ISIS would be most pleased to be the party launching the missile.
For now, ISIS might just settle for a bunch of self-exploders while some public event is being held in or around the Vatican. They got some fancy new, undetectable, body-implanted explosives to try out, you know.