Coincidentally, it kind of simplifies the sorting problem too. Just do like Amazon and don't sort!
Instead, use the machine to figure out exactly what was in that bin you just bought. Give the bin an ID, and store it as is. Then, when putting together a set, have your software find the minimum number of bins you need to pull from to assemble the set. Run them through, and have the machine pull the parts.
- the sets have to be absolutely perfect to be worth something
- you need to check to make sure all parts are present, this is hard enough for Lego which starts from known quantities and brand new parts, with second hand parts and people being ultra picky about such details as year-of-manufacture of the bricks it becomes an intractable problem.
- Rare parts are really rare. In fact, the only parts you would have to document like this are the rare ones, and 'rare' is actually one of the categories that I can sort for. This gives the option to sell only the rare parts for a certain set and to leave the bulk parts to some other method. Much easier to do that profitable.
Said another way, assemble sets around the rare needles you have stumbled across unintentionally while sorting the haystack.