From a purely engineering point of view…
I agree that different natural hairstyles should be considered. But the only things I really see as a potential solution would be sizing helmets up to accommodate more volume, and looking into material development for liners that can compensate for the abrupt changes in pressure that braids and such can create. And its not just the top, the back of the skull needs to be protected too, that has to be taken into consideration.
The problem with this, potentially, could be the cost these materials could be and the effects of extra volume on safety. One of the big discussion points is being able to accommodate people interested in trying the sport that can’t fit in conventional helmets. But if the only way to make helmets to an acceptable safety standard to accommodate for the effects of something like locs, for example, is to use a specially designed material that can overcome the physical effects of impact on that texture, that could still price people out of trying the sport. Simplest solution could be to just size up helmets and use cheaper lining, but there’s the chance that could severely affect the helmet’s safety features.
Some companies definitely should step up and do the research, but people do have to realize that there might not end up being a good answer. Hopefully, with all the advances in material design, it could be figured out, but there’s the chance that there might not be a cost-effective way to accommodate some types of hair while maintaining acceptable safety standards. You can only fight physics so much, and there are always more variables to consider that might not be obvious at first glance. That doesn’t mean nothing should be done, but it’s also not as simple as “they make football helmets for different hair so why can’t they do it for equestrians”. And a company will have to be okay with potentially taking a huge loss in researching and trying to develop a solution to find out it just can’t be done safely, as well as public reaction if the results end up being “we cant do it”. While I don’t think most companies are intentionally trying to block people out of the sport, I also can’t really fault them for not being willing to take a huge financial risk in this environment.
I do think one potential path forward could be crowd funding for research (I think someone else mentioned this). I would absolutely contribute to that.