Yes I have lost on off at the valve. I could put an on off at the pressure source. Off would not be instantaneous. It would take a few seconds for the air to bleed down. Frankly my quick connect is my on off. When you pull the quick connect it bleeds down pretty fast. When you connect, you have a second or so before the air builds up.
I know some will say what a big deal it is to have a dead man but basically the blaster is not that aggressive. Even dropping the end it just flops around a bit.
The real advantage is, when you hold it for a long period of time the less weight and mass is far easier to hold and direct. It is also easier to get into tight spaces.