Castelli came up with the „Unlimited Pro Jersey“ featuring a mesh pocket for a 1.5 l hydration bladder.
I have no idea how fiddly it is getting a bladder in and out for refill (can imagine top racers would rather swap into a complete fresh jersey in an aid zone). Nor how durable (and thus sustainable) the construction is. Nor whether it would actually feel „right“ on your back.
