Here's the suggestion:
Say I have a dyer shop. Make a building so I can attach a container to it so it may use that container directly for its reactions.
In this case, a barrel or a pot, where the material would be specified (one dye type per barrel not to overcomplicate things and to make possible unloading dye bags into it, so the barrel would be filled with dye, and the bags would be freed for other uses)
So, I can build four 1x1 "reagent barrels" right next to the workshop, that the workshop will use directly for its reactions, each barrel with a specific dye; improving the workshop Q reactions would be a good idea, since specifying which dye to use for the reactions would exclude the need of stockpile linking for different dye colors.
These 1x1 reaction containers would act as priority stockpiles, so it could be defined, say "if this container has less than 50% its full capacity, fill it with the desired reagent"; so, dwarves would pick the reagents from any stockpile that has these available and refill the container.
There could be a myriad of implementations to increase control over this, such as having "reserve reagent barrels" in a nearby stockpile, with barrels full of the desired reagent, so instead of simply refilling the container, it could be detached and replaced.
Thing is, this could be applied to most industries that are a pain in the ass to establish, such as dyeing, papermaking, soapmaking and a few others that don't come to mind (cheesemaking maybe? Gem cutting / encrusting? Even symbol sewing)
One craftsdwarf workshop destined for papermaking with reagent bins full of sheet...
One quern with reagent barrels full of pig tails...
One press with reagent barrels full of slurry...
Possibilities are endless and, as I see it, it could reduce by A LOT fps problems regarding the excess of items in a fort since it would substantially reduce the need of individual "dye bags" lying in barrels full of spaghetti stockpile links; instead of 20 dye bags in a barrel, you just get a barrel full of dye, that has x uses before depletion; each use will reduce its contents by x%, based on the containers dimension and on the density/size of its contents. (I guess that in case of stuff that is not liquid a percentage doesn't have to be used, such as a quire bin for a bookbinding shop)
____________________________________________________________________________________________________________
So, I decided to make this a twofold suggestion because I have another one, this one regarding stockpiles and bins/barrels, and problems that arise from them.
For example: I want to have bins in a leather stockpile, but I want each bin to store only ONE type of leather:
Allow per stockpile bin reserving, and allow specifying the materials the bin is gonna receive the same way stockpile materials are specified.
So, I have this leather stockpile, and 3 different types of leather.
So, I will reserve 5 bins for the dog leather, 5 bins for the cat leather and 5 bins for the cow leather. So, they won't mix and cause bugs. If any of the bins are empty, they will belong to that stockpile as long as they are reserved or the tile/stockpile they belong to is removed. Same applies to barrels.
I could be wrong, but most of the bin and barrel related bugs seem to stem from the fact that they sometimes have a bunch of different stuff in them, and stockpiles don't seem to know what to do with it, so it just stays there and requires the d-b-d-k-d method with a provisory dump to be able to free the container and its contents.
____________________________________________________________________________________________________________
I don't think implementing these would be really hard, and I actually believe it would increase overall QoL by a lot. Also would reduce the headache over stockpile linking for establishment of certain industries. Would also reduce the overall number of items in a fort, helping the FPS.