This COULD be done - but the problem is that some water may still (after blowing the system) be trapped in the pressure regulator after you are finished. And blowout is not always 100%, so water movement in lines later after blowout can accumulate in the pressure regulator - which upon freezing can ruin the pressure regulator. It's always best practice to remove pressure regulators from drip systems over the winter. Drip can be easily drained after removing pressure regulators, any valves (ball or gate valves you might have installed - and are VERY prone to freezing damage), irrigation timers, etc. from the system and opening end caps to allow gravity drainage at both ends of the drip supply. Loosely cap both ends of supply lines once drainage has occurred.

If main drip supply lines are drained (manually - with pressurized air), emitters and other components on the line will drain. Small amounts of water remaining in black poly lines will not cause damage upon freezing - but it has to be a small amount of water. Fully full/charged lines that aren't drained at all in the fall WILL be damaged by freezing - as will emitters on those charged/frozen lines.

So, compressed air winterizing of drip isn't necessary - as long as lines are drained and valves, pressure regulators, etc. are removed.

Hope this has been helpful.

Thanks,
tony

Thank you, Tony. 
Your info is very helpful! 
Ben