Mine gets warm too. I once met an embedded engineer in MD who intended to create a more modern HVAC control system on his Evora and sell it, but I never saw anything pop up on the forum. The knob gets hot because it's conducting up to 20 amps of current (fuse C35) through a mechanical switch, and it regulates the fan speed by dumping energy into a voltage divider (notes section SN, p. 52). The resistors heat up as they convert that electrical energy into heat. The contacts inside the switch can also be dirty, adding resistance where it isn't ideal, emitting more energy as heat (and presumably this is the potentially dangerous part, as the resistor package was designed to take it).
2011 NA Evora