Excellent post.
My friend and I were just talking about this very thing the other day.
Especially the part about a RB carrying 300 times a year, VS 2 running backs splitting 150 carries each.
I would love to see something like this in Madden, it would offer another layer of strategy you would need to consider.... Like in my Lions franchise I run Jahvid Best 90% of the time, when in real life that would be unlikely... If there were something in Madden like this, I would need to rely on Smith for more carries since I would wear down Best if I didnt.