Skier 16, I have had an Osia 2 bone conduction implant for a couple of years now. Are you aware that you can test drive the implant by wearing a processor placed over the bone with a headband? It is not quite as strong as having one placed directly into the bone, obviously, but it would give you an idea of how it would sound. Your ENT could fix you up with that. I wear hats and headbands with my processor, but I am not sure how well you would be able to hear with a helmet. Since the processor needs to be somewhat exposed to receive sound, I would think it may not work. Of course the same would be true of any hearing aid that is covered up. I assume it would all depend on the style of the helmet.
I will leave you with this. You do not wear a helmet 24 hours a day, and the benefit you would receive when wearing it during the normal course of your day would be beneficial. Since I am totally deaf on my right side, I cannot determine which direction sound is coming from unless I am wearing it.
Also consider you may be a candidate for a bicross hearing aid. Unfortunately, I was not able to go that route.
Whatever you decide, I wish you the best.