I think a lot of it is determined on what position we are talking about. Shortstop is an extreme example, where playing murton at SS may actually not be as much of a plus because of his limited defense and the amount of action generated by the position. Positions like LF and RF however can get away with putting a player with lesser abilities defensively. I see what you mean, and for some reason think of this example. Lets say we are looking to improve this offense at the trade deadline, and have the opportunity to pick up a third baseman (too early to think of an example). Would moving Aramis to RF, and picking up a good third baseman improve the team overall? Its a very interesting thought, if im on the right track of what your thinking :D