Well, as far as quimera ants the whole thing could be immensely complicated. I do have certain doubts though. The queen we saw made some references to her having some human in her however the whole thing with her was kinda weird. The soldier ants didn't seem to become more human until after the queen started hunting humans herself. It was eating humans that made the soldier ants, royal guards and the king as strong as he was. Now, if there are humans on the outside world then why hasn't a creature of the likes of the king appear more regularly? I mean, all it takes is to eat a human and the whole thing snowballs from there. There are many scenarios to look at in that regard. Perhaps a huge factor is that the world actually is HUGE. If we assume the world killua and gon know is about the size of earth then the assumption we have to make is that the world is hundreds of times larger than our own on a conservative scenario and perhaps larger than that. In that regard, perhaps even if humans or similar creatures exist on the outside then we could assume the world to them is simply so large that there has been little room for them to meet. For all we know the queen was the result of ants running into a lone human thousands and thousands of miles from her home by accident. Perhaps the queen was the result of a primitive human too (missing link idea). Another thing is that if we take a look the queen actually was very hurt when we first saw her. Have we ever bothered to question who did that to the queen? If she came from the outside then I can see two possibilities. The first is that it was humans or human like species dealing with the ants due to the danger they can represent. The other idea, and perhaps the one I favor, is that it was other ants, one that perhaps had a chance to evolve just a step further than the queen earlier.
Now, if there are quimera ants on the outside then the logical conclusion is that there are a few of them to say the least. Considering the description given originally there are bound to be several queens wanting to give birth to the strongest king. Now, in an overwhelmingly large world with human like creatures it is entirely possible that quimera ants could develop independently from humans and become strong (although perhaps without nen as the ants only learned it after actually seeing it). Now, if there are several queens who birth several kinds then the logical thing to do for those guys would be to battle it out. After all, the prime directive behind a king and the royal guard is to be at the top and keep evolving. In this regard it is nothing but likely that quimera ants are at war with each other over there in a very yu yu hakusho 3 kings kinda manner lol. If this is the case then it would explain what happened to the queen that got to the known world. She, perhaps with the previous generation of king, battled it out, they lost and she managed to scape on her own. Now, these ants would still not be necessarily as strong as mereum. They would need human quality food for that.