I think the idea behind random slaves is really interesting, but the implenentation has something missing. Right now, they have nothing exciting about them, and their scenes are basically cropped images of scenes with the unique slaves. After playing with the random slave generator for a bit I can say they are not interesting to train or acquire as they add nothing zero personality compared to uniques. I would never waste a slot on a random slave when I could be acquiring a unique.
I know that generating renders for each body type combination is impossible work for a team let alone 1 man, but there is really something missing to make them desrible to fill a slot in the house.
My only recommendation is to work on a set of renders unique especially to the random slaves, a hundred set or so that all of them can use.