With an e-bike some of the potential energy on a descent could be captured and used to recharge the battery.
Here's an interesting read. I subscribe to the German magazine Tour. It's a technically-oriented cycling magazine....similar to Consumer Reports but it's 100% dedicated to cycling products. They tested the previous version of Shimano's Ice-Tech 160mm rotors on a single bike and they failed spectacularly. The aluminum core that is sandwiched inside the stainless steel braking surface had melted and the disk collapsed. Recently they tested the latest improved Dura Ace 160mm rotors and the front brake also failed but it didn't collapse like the previous version. Their conclusion was that the new design was a significant improvement over the previous version. However they caution that heavy riders will likely push the new version to its limits. The test was done with a 220lb system weight (bike plus rider) with a 245 meters altitude loss at a 13% average gradient.
This goes to show how big of challenge it is to design a braking system that is both capable and light enough for every day use, for a single bike!