If we were you, we would quit now.
Quote from Oginam:
Do blueprints include all the ones that are used to modify weapons? Are any of those random purchases from vendors?
According to this: http://gaminggix.com/dying-light/dying-light-blueprint-locations-map-and-list-view/
Quote:
some can be bought from shops at a certain point of the game (or level)
So, it doesn't sound like they are random, but you'd actually need to progress in Survivor level to get them. You might be able to dupe different groups of relief packages and force Survivor leveling accordingly to allow the blueprints to be purchased at relatively the same time near the start of the run. Then, you don't need to worry about Survivor level after that point.