wide trail
Each decider takes input of various quality of rocks and holmium ore and outputs their respective recipe quality.
A selector then sorts the recipe to be used starting from the highest quality descending.
Problem is when the recipe changes while there are still some leftover ingredients in the plant (i.e a rares came in the supply when the plant is still processing uncommons. Is this even scalable considering epic and legendary qualities?
gentle perch
Each decider takes input of various quality of rocks and holmium ore and outputs...
You might be able to do this by limiting inserter stack size to the amount in a craft, and then having a disable signal when there aren't sufficient items - when the machine is read empty by a combinator then you switch quality (filter for "any quality" of each item)