Good point, Nate. The nature of the crushing surface on these home-use grain mills (and how that would affect the coffee grinds) did cross my mind.
I suppose this thread was more of a conceptual exercise, which could have potential lead to some (probably disastrous) DIY projects. I wonder if home/café grinder manufacturers have ever considered trying to make a small scale roller mill. I don't think that there would really be a need for a roller cooling mechanism similar to what Alan mentioned, given the relatively small amount of grinding it would do. Though as Tom pointed out, it might end up having several sets of rollers in decreasing order of grind size.
In the end though, it just seems as though the nature of roasted coffee makes the production of fines during grinding inevitable. Perhaps a wet grinding, home-use dual grinder/brewer? This grinder is becoming more and more convoluted in my mind!
"Really great things are evident to anybody who's paying attention." - Charles Babinski