Since you dont mention what excatly you're refering to in regards to what you've seen from the Nier team, I'll take a wild guess and consider the panel at the FanFest and Yoko Taros quote about how hes going to take down FFXIV with when his downfall in 2019 will begin.
...and if that guess is even remotely close to the truth, I have to ask: Dont you see how thats supposed to either be a joke or just provoke? Have you seen how Yoko Taro presents himself when it comes to things like this panel? The man obviously likes to enact himself as some sort of mad genuis type, so taking his words at face value is... questionable and something I would refrain from.
I dont see how a Nier-inspired setting cant fit into FFXIV - a secret base in/on the moon/somewhere in space? Check, had that since FFIV, had it again in FFXIV. Giant factory-ruins? Check, lets have a chat with allag! Androids? Well, we already have all those little mammets, some with more personality than you'd expect from a maschine - Gigi (goldsmith) and Gigi (aka Vivi) would like to have some words with you! Fighting robots/maschines? Thats basically the whole Alexander-raid... Menkind being (almost) dead and earth being destoryed? Yep, thats the First for you...
To me a Nier-crossover seems to fit better than the whole FFXV-stuff we got - riding a giant moose fits way better into Eorzea/FFXIV than the Regalia.
I wouldnt take Yoko Taros words at face value, thats just naive. And I would have faith in our dev- and lore-team to keep an eye on the addition of Nier.