The IH&AS was really just an idea I had for why investigators would keep going to the far-flung corners of the world. If you're running the adventures in AoC 5 as individual, stand-alone adventures, that's not so important ... but if you're connecting them in a campaign, or connecting them to the earlier AoC modules, I thought the Society would help explain the constant trips around the world.
I sort of envisioned it at this murky, secretive organization with plenty of hidden agendas. Not to mention lots of connections, which would help investigators find NPC connections in distant locales, or obtain necessary documents/paperwork, etc. How helpful (or not) the IA&HS is (or isn't) to investigators is ultimately up to the Keeper.
I don't know if there's any plans to expand on the idea, but it's good to know you guys like the concept.