You're not going to find an AWR authorizing anything but the flight helmet for use. There have been misinformed but well-intentioned people who have tried this many times over the years. The ground situation has not changed, contrary to popular belief. People have been shooting at helicopters and the people carrying them since day one of the current fight. Everyone wants to revisit this topic during their deployment because it's scary when fuckers shoot at them.
The in-flight portion of the fight is by far the most dangerous. Good comms are essential to everyone surviving the flight. The flight helmet accomplishes this.
Not to be a dick but, if shit is sketchy when you are on the ground feel free to swap helmets or just hope for the best. The only time I would swap helmets was if I was on the ground for a significant amount of time. (more than 30-45 minutes) Speed is safety and not fiddle-fucking around with things when you should be getting back into the air ASAP will keep you safer. I'm not a medic nor have I done medevac stuff, but I have been around this block. The army SOF aviation guys are wearing flight helmets. People see TV shows with PJ's and want to emulate but they are just passengers. The Army doesn't condone or allow anything but the flight helmet.