FWIIW, people say peripheral vision is extremely important to hockey, and that is what limits hockey helmets. One hockey guy, who learned before helmets came into general hockey use, told me that even the helmets that are transparent fog up, blocking visibility. If you use chemicals to prevent fogging, the condensed sweat just creates a lot of water droplets on the surface that interferes with vision too. That's the reason, so he says, that pro hockey players usually wear very minimal helmets, that provide relatively little protection. He claimed that even the hard wire mesh at the front of hockey helmets interferes somewhat with vision and hockey play.
But you also need to remember that the primary thing that hockey helmets protect you against are fast flying puck impacts to the eyes. A situation rarely encountered by figure skaters in public and freestyle sessions, unless you skate at a very poorly managed ice rink.
Construction workers are most worried about heavy falling objects hitting the top of their heads.
I think speed skaters mostly worry about other skaters running into them with their skates when they are down on the ice.
I think figure skaters are most in danger (for their head) of getting their heads hurt by hitting the back of their heads on the ice, and perhaps secondarily, forehead and chin impacts on the ice - both in falls. And in fact, all the times I have seen a skater hurt who wasn't playing with sticks and pucks, it has been to the back of their heads, after falling stiffly backwards.
I think that many so-called-experts who try to develop standards for a general purpose protective helmet don't take into account that different sports tend to involve different risks - and that protective gear that protects against every possible threat in all activities will be too cumbersome and uncomfortable to be used. There is no reason why the same types of protective gear should be optimal for these very different situations, so we can mostly ignore helmet ratings designed for other activities.
E.g., if I'm right, soft compressibility at the back of the head, not hard shell abrasion resistance, is pretty much all that matters to us.
My personal intuition, which may be wrong, is that something like the Ice Halo HD
, which resembles a head-band and only cushions the top-back part of the head, not the central-back part of the head, may only offer borderline protection to figure skaters.
I'd bet that if you took a thin ski cap, and sewed two layers of foam - one open cell foam, one closed cell foam - into the back, it would do all you are mostly likely to need. Maybe even just the closed cell foam - e.g., carpet foam, say a 4" tall by 6" wide piece, for an average size adult. You might be able to get a scrap piece that you can cut down to that size from a carpet store, for $1 or $2 - though the salesperson may not consider it worth their time. BTW, carpet stores can also sell you open cell foam, if you want to use two layers.
BTW, the foam in my suggested design would serve two purposes - first, the gradual compression would reduce the deceleration suffered by the head when you fall backwards. Second, it would help prevent you from rolling the cap up too high to provide protection to the back of the head.
But even that suggested design will cover enough of the head to make it harder to get rid of sweat and heat. And a lot of figure skaters, particularly ladies, care a lot about how they look, and may not want any portion of their head, especially the front and sides, covered - so it's far from perfect.