Think the real problem here is with the insurance companies not Mercedes?
A certain proportion of cars [Including Mercedes] will go on fire.
A certain proportion of car owners will deliberately set fire to their cars.
Many insurance companies will try to avoid their responsibilities and pay out
There's been a problem with Mercedes catching fire for some time, Mercedes have kept it quiet, that's why some of these cars get replaced under warrenty and not by insurance payout.
Interesting to note that the fire started from the car's boot.
Could this be the answer? I have been told that on my W124, the rear number plate lights are not fused and with the opening and closing of the boot lid over time, the wiring weakens and does break leading to a possible electrical short.
Could it be the main battery, I once had a loan C Class W204 diesil from the main dealer which had it main battery in the boot.Thinking back it was quite a noisey car in side, I remember thinking give me back my compressor.