An interesting thing about this is that it was mentioned the client was asking for Archons specifically, due to their neutrality.
That means whoever the client is, they are at least loosely connected to, affected by, or aware of Eorzean politics. Or they are aware of the Scions’ false retirement and they are trying to get in touch while not raising any eyebrows.
That, plus Erenville’s mention of a homecoming, would initially make me think of the blank spots of Ilsabard and Western Othard. We still have mysteries there like the flying whale, floating islands, and the giant.
The New World does have connections to Limsa Lominsa since they’re their first and seemingly only connection to the 3 great continents. Limsa/La Noscea has a sizable population of New World immigrants too.
Meracydia has no connections in ARR canon. In 1.0 they had trade with Limsa Lominsa but I haven’t seen that come up since. But I’m also biased against Meracydia since I live in a desert IRL and feel like we’ve had enough of that aesthetic in ARR, SB, and ShB.