There have been a lot of products that used carbon over aluminum, ACCs were relatively late in the game. Ski poles, and ice axes were early in my experience, though I am sure there were others (leaving planes aside for the moment). ACCs are interesting in that they used this approach in order to get more accuracy/consistency. With the other products it was partly to deal with early hoop failures, and partly to deal with vibration. Ice axes are a nightmare if they vibrate, not only do they buzz your hands, but they can shatter the ice you are trying to gain purchase in. These days there are a lot of ways of dealing with vibration.

When it comes to these kind of what if scenarios, the thing is to have something in mind, and then ask what is the technology that would make it possible rather than starting with the structural solution in mind.

If, as has been said, the very light HCAs want to go for the gold along with the arrow, then that is all the more reason for them to build a C2 (or Patriot, Q2XL, or whatever).

Hey wait a second, McPhersen, I have heard that name before, so when does Mathews debu its carbon technology?