IMHO the FSM could look something like this.
2 different AI modes: offensive, defensive.
Defensive - scan visible areas for opfor, look for cover. May or may not keep moving. May try to move to highest point/furthest point from entrance.
Offensive - scan visible areas for opfor, always moving to next "open" building position that isn't already occupied by friendlies. Array of building positions tracked so that as each is cleared, it is ignored by friendlies. When no more positions in array, unit is released for next building or waypoint.