if it wasn't a really hot fire and only burn part of a wiring harness, then you might have a deal BUT, the s250 has a plastic fuel tank, and hydraulic tank, and LOTS of plastic parts around the fan, engine, and radiators.
I had a small fire and in two minutes it burned a hole in my fuel tank costing me about 2 weeks down time and my deductible. The fire didn't get hot enough to hurt anything else LUCKILY.
I'd be very cautious. An '08 s250 is about as complicated as a car's wiring and will be a headache to replace. It is probably dealer territory since you will need their software to recalibrate things if the computer is damaged, shorted, etc. Again, I wouldn't look at it for anything other than scrap unless it was a small fire that ONLY affected the wiring in a specific area. Anything else has too many unknowns and like someone else pointed out, a hot fire can weaken structural integrity plus if this thing was doused you could have water in motor if the upper rubber assemblies around the air intakes melted and someone dumped a fire hose on it.
"Life is tough, but it's tougher if you're stupid."