Sorry to necro this thread, but it is one of the first results in googling "factorio mixed quality" that comes up.

I would like to see this for 2.1 ideally, even if only an optional mod-enabled feature.

The requirement that assemblers and so forth only accept one quality level makes engaging with ...

I agree on this one. It should be based on the quality of the factory making it somehow. next_probability could still come into play as a multiplier if need be, as well as next_probability_scale.

The calculation would look like:

next_probability + next_probability_scale * factory.bonus_quality ...

I noticed either a balancing bug or prereq bug.

Utility science pack requires silver-zinc batteries, but only requires lithium-ion battery tech.

Seems it should either be lithium-ion item -> utility pack item or silver-zinc tech -> utility tech.

Similarly battery-3 (silver-zinc) requires ...