Sorry, but this doesn't really appeal to me. I imagine it would be a lot more uncomfortable than my current Rift, and would probably have significant fogging issues with the screen (because of exhaling inside the helmet). Also, as other have pointed out, it would be even more difficult to eat/drink while wearing a helmet.
One other major issue I see is that an actual motorcycle helmet comes in multiple sizes in order to fit the wearer correctly. You would also need to consider this. But if you made different size helmets, it would be unlikely that I could share it with other friends and family.
One other last thing that affects me, but not everyone, is the issue of wearing glasses inside the helmet. A real motorcycle helmet has a visor that you can lift to fit/adjust your glasses. With the VR helmet, this seems unlikely and would probably mean that I couldn't wear glasses at all while in VR.
So, sorry to throw all these negatives at you, but I think you really need to think about the practical nature of the VR helmet before investing any money in developing one. I don't see how this could work for me, but I wish you all the luck in your endeavours.
o7