I don't know how most trades work but I was wondering if instead of failing at a trade and not getting anything, plus losing the items if it would be possible to have failed items. For example when fletching instead of losing the whole lot you get a "not so true arrow" or something like a stick with few too many gouges, a ruin feather, and your arrow head. For tanning, armour and weapon making: a piece of hide with splotches on it or a brittle piece of hide; arm sized leg guards or parchment thick armor; not so balanced longsword or a dagger with many notches still in it. For lapidary maybe mismatch diamond earrings or and oval shaped ring made of gold. If you don't like any of those ideas, instead of all new items we use the current successes with poor or awful instead of perfect (for armour you would take it then to a professional to fix it).
They were just ideas. Things that would be not worth more than a few coppers but possibly things in which people could rp their trade levels. I don't know how it would work or if people would discard them all about the place but then maybe a mob could collect them turn them into pieces of metal or wood. Possibly if someone does litter too much such could be done to require a fine, the stocks in MS or imprisonment (I bet everyone will be against it now).
Maline