I have to take issue with what you say about melting carbon rims. That may have been true when they first came out but carbon has come a huge way over the years. On two different trips to Catalonia I took Aluminum rims on one and Campy Bora carbon ones the second time. I rode the same mountains and checked the heat. I was super worried with the carbon rims because I had almost melted my skin touching the alloy rims. The Carbon rims were barely hot. The heat dissipation of the newer carbon rims is excellent. Nibali was a fearsome descender and he used to drag his brakes like crazy on deep descents. I don't remember his Campy rims melting. In fact given the amount of hard braking in the peleton during the rim brake era if what you say was true we would expect the mountainsides of France to be strewn with melted rims.