So what on_headset is telling us is they commit the cardinal sin of headset use and press the talk button prior to screaming hold.
The cardinal sin of sitting in a soundpoof booth a few dozen meters away from the actor who's about to get squashed? (In a house where, I might add, cellphones don't work anyway.)
But again, wouldn't a god mic be more useful then? What happens if someone is off headset? You can tell them hold all you want. For the example you're giving, a god mic is the best tool. It's a direct line to the sm and it goes through the sound system.
Now, I may be misunderstanding how your set up works. Headsets can tie into the sound system i realize that. But if you're calling hold through a relay of people, that's not exactly a plus.