I think that you're over thinking this ..
If you want to tie up some spinners with egg cases, a little yellow ball of dubbing at the tip of the abdomen will take care of that.
As for "defective" molting duns? You could try a trailing shuck of zelon or antron or even a little wisp of nylon panty hose
. Maybe with one wing up-right and one rolled, stunted or horizontal.
Just having some scissors to cut your normal dun imitation down is probably the best way to go rather than tie up something special