You wouldn't be fixing the problem, you would only be changing it...
Ok, let's say that the three Kings(KB/Aspid/Nid) and their lesser forms require you to farm a pop item in order for you to spawn then. Assuming the pop item would be rare, and drop off of decently high level monsters, people would need to kill them with 6 or more people.
So you've got your party up in Boyahda Tree and you're killing Marboroloros, for example, that drop the item for Fafnir. Another party shows up and starts killing them too. All of a sudden they're all dead, and you find yourself competing for Marboroloro instead of Fafnir...
Not to mention the main problem with HNMs is not claiming, it's people stealing them when hate transfers between parties in an alliance.