Look at what has been done with the RS4 as well. Specs quite similar to the E92 M3, it can handle turbo or supercharging. Longevity is of course the big question. As far as the tranny I bet the exact same tranny from the M3 gets on to the new M5, it will probably have in the neighborhood of 420 ft lb (very rough guess - not following development there much at all) and since it is rated for 440 ft lb that should be completely fine.
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