I don't think we need to go quite to that extreme to foresee that most people who have a fundamental objection to wearing facemasks - whether the objection is based on religion, essential oils, crystals, voices in their head or a belief that Covid-19 is a means by which to implement some form of world government - is going to resist and ignore requests from the constabulary to wear a facemask.
After that, it's not that hard to foresee that the constabulary are either going to have to arrest or retreat. Being appropriately prepared for an arrest seems like a pretty obvious planning step, including the use of proper PPE, for the constabulary in the circumstances.
So next time I become SLF, I shall expect the cabin crew to be in full PPE.