You have to have 2 units. One normal and one "SS" as you say. One will be hidden while the other is in play. When there is a chat event, such as a player typing "ss," as in "event- chat event: entered chat string is equalt to ss" you then have a action like "unit- replace unit," moving the ss hero to the postion of the normal one and unpausing, unhiding, ect, and move the normal one out and hide/pause him.
-VGsatomi