Thanks. Helmet design in this respect looks like a dead end. Giro (Switchblade) and Met (Parachute) do detachable face guards that look the business and get good reviews.

The types of injury thing something i'm looking into.

One idea that has just popped into my head is that of a connected helmet and upper body protection. One that is very loose at all times to allow ease of movement. Has some kind of connection to the bike somewhere that if it is broken the suit will stiffen to protect the vunerable neck area. Similar in a way to the cord that can be attached to yourself when on a running machine that applies an emergency brake if it comes out. Hmm....