Some offshore sailors add a removable inner forestay in order to fly a smaller head sail and to have a large headsail. The loads on the stay are significant, the deck fitting needs some engineering to properly distribute the loads. The deck structure is usually too weak to accept the loads without major work.
For these offshore sailors, the advantage to a removable forestay and head sail is to move the center of effort aft when the mainsail is deeply reefed. When it is blowing 25+k moving the center of effort makes a huge improvement in boat comfort and handling.