Surely there must be a raft of regulations somewhere that specifies the correct clothing to be worn for flying duties - there certainly was in my day [up until a few years ago]. You can't willy-nilly change the regs - after all, flying kit [inc cabbage flying kit] is specifically designed for working aircrew to wear in the aircraft. The chopper back-end is designed to carry non-flying kitted people, so if buttons, etc, get torn off it won't affect the operation of the ac, but might do in the cockpit.
I suggest a Condor, or a call to the big white chief, flight safety [whatever he is now called] is in order - I'd certainly make that call Monday morning if it was me at the receiving end of a lunatic decision like that. What's your unit FSO doing about it?