The character things, though, aren't always easy to quantify in a useful way. I'm sure you could quantify all the aberrations in a Heliar at f:4.5, for instance, but it would be difficult to translate that into a visual description of what the lens looks like when used for portraits at a certain subject distance range.
A conventional list of items "to avoid" would probably be useful to someone with a Sally Mann or Mark Tucker sensibility as well, because they might want to see what happens when you use precisely those lenses that are to be avoided. Many of the Sally Mann lenses were damaged lenses, maybe with a cell missing or separation or severe surface damage--lenses about which no useful predictions could be made, and the same goes for loupes, eyeglasses, magnifying glasses, Holgas and such. The chance element is part of the attraction.