I'm wheighging in late on this, I know, but that's because the conversation was on swords and Witcher lore, and I know little of both.
I think one of the ideas that makes more sense to me is the first. Like he is gathering his kin, but he also doesn't want them to be just taken by foorce, so he makes the fake contract to attract people and then convinces them of taking part on the hunt for the sake of the puny humans. Also, he can bluff his way out of the king sayin something like "Yes, this are totally the last there are, you should belive me, I'm a Witcher."