I'm not sure it's that easy. Plotters are functionally different from printers, and that creates problems. Think of it this way: you have plotters, which pretty much exect data to be sent as a vector format. Similar to PostScript, right? Well, not really. At the end of the day, every printer will rasterize the data. Sometimes it is done by the computer. Sometimes it is done by the printer. So if a printer is told to draw a line that is 2 points wide, it doesn't matter since it is eventually rasterized.
But plotters just draw lines. They don't care about the thickness of the line because they cannot do anything about it (short of using another pen). I have seen some software bugger this up royally, and actually send two lines to represent the inner and outer edge of a curve. Which, I suspect, is why every program that I have used has come with some sort of plot-manager and its own set of drivers.