I would highly encourage you folks to stick with the strict "X/Y" nature of the reach/stack nomenclature. You spent a lot of effort explaining pad and bar stack and reach in that .pdf, and to then "revert" back to "stem length and angle" on a part that really is just another "X/Y" locator is fairly confusing IMHO (edit: especially when you call it "reach" when you mean "length"). Then again, the stack and reach contribution of each stem will be different depending on the frame size due to the varying head tube angles...so maybe using stack/reach isn't possible to "name" the stems...hmmmm.
I agree, the "descriptive" names are probably clearer, just as the XS, S, M, etc. frame size names are used. As long as the chart gives you the final touchpoint locations (i.e. pad bar stack/reach) then all should be good.
http://bikeblather.blogspot.com/