As for the engine, I´m pretty sure a current DTM engine (dunno about the 2012 spec) can do a 24h race without much problems. Audi and Opel both raced at the 24h Nürbugring in 2003/2004 with their DTM cars.
Sure they where modified a bit (using ABS and later paddle shifht etc.) but at least the Audi used a more or less standard DTM engine. We could run larger restrictors at the 24h, so their are some differences in the mapping and a little bit different camshafts, but nothing big. A DTM gearbox is a bit of an issue if you don´t use paddle shift, in 2003 both Audi and Opel had gearbox failures during the race, but with an automated system (Megaline) in 2004 it was no issue.
The cars raced ~200kg havier then DTM spec and on more tank volume 100 ltr vs. 70lr, and where competetive against and GT2 BMW (M3 GTR).
So depending on the "battle of performance" regs, I could see a possibility to do it.
It will depend on the "fine print" of the regs.
Having said all this, a 2002 DTM car is a far cray from a 2010/2011 DTM car as far as aero goes. A 2002/2003 car is not that far away from a GT2 car IMO.
I think a current DTM car, would struggle to last 24h, at least at the Nürburgring, and the cars are in no way service friendly.
Nevertheless, for an DTM engine it should not be a problem to run 24h.
But they are maybe a bit underpowered compare to some GT2 cars.
I can´t see Mercedes coming back to LeMans in a hurry, but that´s just my opinion, and I could be wrong.
"Make the suspension adjustable and they will adjust it wrong ......
look what they can do to a carburetor in just a few moments of stupidity with a screwdriver." - Colin Chapman
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