Try googling 'NFL collarbone injury', and then look at the amount of padding those guys wear.I feel that you have some vision of medieval armor in your head. But even with that variant it could i guess be done. That is to preserve full mobility of i am guessing a shoulder joint. As you assume shoulder wouldn't be able to move after?
And don't you feel that the shoulder is close enough to be considered as a part of the same area?
Who knows. Maybe cyclists would learn to use such apparel to break the fall differently. Compared to what they are doing now. When they know the apparel isn't offering them any advantage.
Seeing as you keep calling for apparel manufacturers to create something but have no ideas of your own, how about admitting that maybe - just maybe - this is something that apparel manufacturers, riders, organisers and sport governing bodies have already considered, but without being able to find a solution that doesn't also badly compromise the riders? The thing is, riders need the flexibility and dexterity to help them avoid crashes in the first place. It's no good preventing collarbone injuries in x % of crashes if you then cause the number of crashes to go up and neutralise that benefit.