I forgot to mention that the base-item highlighted (when you look at the materials stocked in a workshop) for dumping/forbidding also happens in-game normally as well when mass-dumping/forbidding through the stocks screen. That was where I originally noticed it; and sometimes it tends to shut off the workshops (nobody claims them for any assigned work or moods), but not leave notifications of such jobs being "cancelled" (because how can something be cancelled if it isn't listed as available to claim in the first place?), and I have to manually hunt each workshop down and un-mark them for forbid/dump. Usually after every material has been dumped, and we still have a few "stray" material blocks laying around, and you can't find them (only for them to be the workshops/trade depots themselves), or be able to process more materials because the buildings have been 'denied access' in the process.
I can imagine it can get really inconvenient if you have an old fort which is also industry-focused (30+ dedicated workshops, let's say; and you're sorting out (or quantum stockpiling) tons of materials (or of a material) between stockpiles/dump sites), and a couple shops just stop being claimed 'inexplicably'.
One solution I have in mind is that it's generally the first item (and first 3 if a trade depot or larger workshop/building) in the list that is the base-material the workshop is made of. Should be as easy as clearing the first slot in all workshops or something like that when mass-dump-optimizing. Another solution is to auto-unforbid/undump all workshops (but might include their inventory unforbidden/dumped). Kinda like when using the mass-dump/forbid cursor, and you highlight over a workshop, and it glows green or purple, depending on the command (must be at least 1/2 the size of the workshop/depot in order to highlight it completely with the mass-highlight-command).
That's more about what I noticed.
EDIT:
Regarding the other idea(s). It would be interesting to dump things of specific item type, quality, material (obviously) and value range. So you can have specified dump zones (auto-forbidden, and left forbidden until trade time comes, and being a quantum stockpile, it's really easy now to mass-un/forbid them between trades) or stockpiles dedicated to a value range, than just quality range. Great for the picky or OCD bookkeeper/trader. However, it can be really practical to use when sorting things out for trade or construction/workshop projects. Two piles parallel to each other, one is total crap to sell off instead of incinerate or atom-smashing (and ease pressure off the other stockpiles by acting as filler; or vice-versa, and do those instead of trading), and the other is the finest non-artifact stuff (even if not super-fine quality) for a quick buck.
And naturally, we can have it like DwarfTherapist, and have pre-settings/templates we can inject into other stockpiles (like profiles in DT). Naturally, there would be the popular pre-sortings like "Artifact Pile" (nothing but artifact quality goods), "Useful Refuse" (Like bones and such that can be crafted still, or used for other purposes), "Useless Refuse" (You know the kinds, absolutely broken goods, rotten goods, unusable leftover flesh, etc.; leave them out to rot or disintegrate, or make miasma pits). "Bottom-tier Trade" along with "mid-teir" and "top-teir", depending on mood or who to trade with. "Wood-based trade goods" and "non-wood-based trade goods" in case you deal with elves often; and of course "Non-trade items/furniture" (what most people aren't willing to trade in any case). The list goes on.
And if possible at all, have an option not previously available in the stocks/stockpile screen and allow wood to be sorted in different stockpiles, since stone can, but not woods (unless I didn't notice that get remedied already). That was something that bugged me when working on my airship. I couldn't be specific on what wood to use per-section more easily (all wood was in the same stockpile, and I had to remember the name; and I couldn't just mass-forbid either, because then all the 'general' wood gets highlighted, instead of a specific species). Had I been working with fungiwood (colorful plants as well), this could've become a bit of a problem, and I would end up with a technicolor ship.
Consider that as another option to have available; provided the right flags/raws can be found/used in the highlighting or choosing for dump and/or stockpile. Sorting by color (based on what we already know or what's readily available about the materials at hand (generally raws and such)). I know those with aesthetics (or a total OCD nutcase) in mind will find that really useful. Further sorting based on RAW (file's) information of the items/creatures and so forth. From color, to weight, base value, and so on.
If an idea like this is worth doing (or thinking through), it's worth overdoing it. Provided plausible boundaries, of course.
Done gatling-editing now.