P40DC

What makes a P40DC unsuitable (or undesirable) for freight duty? I know that lacking front and back platforms is one problem, but what are the others? (I was thinking of medium weight trains and gentle grades.)
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103 mph passenger gearing for one.
Monoque carbody without frame beams for suport.

A freight loco is more than 100,000 lbs heavier than a passanger one (less tractive effort). Also, running "long hood forward" would be impractible; you would have to run in pair with another loco as the MM&A does with its F40.