So to skip the beating around the bush and step-by-step... what I was getting at, Shade, was that there's nothing to draw intelligence from in ModelSpace that would tell you HOW to scale the linetype so it shows as it does on paper. You'd have to pull the plot scale from somewhere.
If you dimension in model space, you could pull this scale from the current DIMSCALE, but that has flaws, even.
If you use paperspace for dimensions and/or plotting, then you pretty much have to see it there, only, like Krush and the rest had expanded on.
I guess you -could- somehow write an LSP or VB or ARX... that could get the values of any viewports it finds in any layout tabs, and then let you select what scale to display, and then set the scale to multiply the LWT display scale by... having it set to display in the manner CmdrDuh pointed out with his 'display plot style' tip.
I don't have the talent or knowledge to be able to write such a thing, or to verify if it'd even WORK... just thinking with my butt I guess.