Scratch the pages, books, and libraries. Let's just have fragments.

Each item could have a fragment value and you could research what you want with your fragments. Hatchet would be 100, AK 1000, c4 3000, etc.

Or since it’s become way too easy to get blueprints now with this new system, we get rid of the upgrades like you say but fragments are only used to boost the chance on research tables and the items remain in the tier system so you need more fragments to increase chance on better items but we also cap the chance at like 75%. Long sentence.