I wouldn't like to begin to speculate on the cause of death but the overheat/boiled to death scenario does hold water.
Fluid friction and pressure can cause very high temperatures in hydraulic pipes along with conducted heat from the hydraulic pumps. This is why hydraulic systems have coolers and reservoirs which are designed to dissapate heat. It is a prerequisite of a hydraulic fluid to have a very high flash point for the previously mentioned reasons.
In addition to that brake temperatures do become exceedingly hot and dependant on the material retain that heat for a longer or shorter period of time. None the less pre take off brake temperatures will exceed aftertake off temps due to friction. Not only does turning and braking etc add to the temperature but the take off roll itself will increase it.
Brakes have no 'real' release mechanism, the realease relies on the fact that there is no further pressure on them. So even without the brakes applied there is a conciderable amount of force on the actuators and pads after braking. (say for arguments sake the braking force often applied during line up).
Try applying the brakes in your car, then remove a wheel and try to turn the brake disk, initially it is near enough impossible even if you didn't have the engine running and the servo opperating when you pressed the peddle.
So until pressure equalizes in the system or a microscopic layer of brake lining wears off or a combination of the two there will be alot of friction even during take off and therefore a lot of heat generated.
I have to make an assumption now that the amount of heat that rubber. used in the manufacture of aircraft tyres is far greater than any human can withstand for any length of time. Therefore personaly I have to say that it is entirely possible that this person could well have died due to the heat in the early portion of the flight well before he suffered the PD/Hypoxia/Freezing theories.