Registering the actions to level the weapon sounds like a combination of organic and targeted work.

We'll see some actions as we level as stuff drops from the mobs that opens them. Then to get the rare ones people will need to form hunt parties to kill the lesser killed stuff to get the pieces for those actions. Toss in some RNG from the combiner and it seems like a process that will be a tiny annoying, but not light grinding level annoying.