The Life Safety Code requires a written plan for this condition. The number of falls from a stage is significant. I researched fires on stages and in about 20% fire service were injured when they fell off the stage. I specify a temporary guard - usually netting attached to proscenium. Most professionals erect temporary guards for set ups, etc Most of the falls I have seen or heard reported are not performers, but workers or people not usually on a stage. Worst in my memory are college presidents and trustees "touring". Warnings and instruction are helpful. And just like people are not permitted in a factory or lab or construction site at least without some protection, a stage should be treated the same.
So, the front of the stage is a code exception to guards as are openings within the stage, but a hazard that the owner should know of and be addressed.
