I threw together a quick Python script to merge multiple Eeschema libraries into one - here it is if anybody wants something similar:
https://gist.github.com/cpavlina/dc0bf5f5c018d43fa736
Keep in mind it’s just a quick script, don’t be too hard on it. 
Use it like…
kicat.py -o diodes-generic diodes-1N diodes-BA diodes-MMB
…for example to merge diodes-1N, diodes-BA, and diodes-MMB into diodes-generic.