First of all, for clarification, uhm. The Z is being used as a pro-war symbol. It's painted on the tanks and has been frequently used by Russians to show support for the war. (Or rather, support for their victory; they probably don't want to prolong it, they just want to win it.) That's the actual reason Blizzard made some moves in response. The Guardian's got a good overview, but in short nobody's 100% sure on the exact origin point, although we're all clear on the meaning being used.

I completely agree with both Blizzard removing the Z from Overwatch outfits and Nintendo delaying Advance Wars, but that's actually because they hit closer than they were comfortable with hitting. The Z outfits in Overwatch were not only the exact Z being used on the tanks, but also on the Russian character; that hits uncomfortably close for people and we're better off not having it if we don't have to. Similarly, Advance Wars wasn't postponed because 'it's war and it'd be in bad taste', but because the actual story of Advance Wars is about an obvious Russian-analog making a military push into a westward nation; that's probably not a game you want releasing right now, no matter how obviously Cold War the aesthetic is.

But the Z title in FFXIV... it's just a Z. While I would hardly begrudge the developers changing it to 'Zeta' if they wanted to keep the Zeta Gundam reference while avoiding this, I don't think there's really cause to remove a title that's just a letter unless there's a significant amount of people using it for that. And frankly, I don't think I can remember the last time I've seen anyone use that title at all, so it's probably not being used very hard.