TL;DR
Improve customizability of how modded recipes interact with the new Quality system.What ?
Add new quality related fields to LuaRecipePrototype allowing greater customizability of Quality system on a per recipe basis.Add a minimum_quality field to ItemIngredientPrototype. Below this doesn't qualify for the recipe. This is the baseline, so only quality above this level adds to the quality of the result.
Add a quality_weight field to ItemIngredientPrototype. If set then the quality of this ingredient has more or less impact relative to other ingredients on the overall result quality.
Add a quality_bonus field to ItemProductPrototype. If set this output of the recipe has a higher quality baseline. This isn't random and doesn't have a chance of resulting in even higher quality tiers.