TL;DR
Allow on-the-fly substitutions for items in blueprints (ie. place red belt instead of yellow)What ?
Add boxes below each item listed in the edit blueprint interface (the ones that list the number of each item in the blueprint) that work like an inventory filter, and let you choose a new item (with the same footprint) that will be substituted for the corresponding item when the blueprint is placed (but does not actually modify the blueprint). The blueprint would remember these settings.Why ?
This would drastically reduce the number of blueprints needed. Instead of having "XYZ production block with yellow belt and standard inserters", "XYZ production block with red belt and standard inserters", "XYZ production block with red belt and fast inserters," and so on, you'd have one "XYZ production block", and could modify the inserters and assembler/belt tiers based on what you have researched/available at the time of placement.This way, you can use the same blueprints as you progress through the tech, updating individual items as they're researched and/or automated.