Doubt it would work, IP being one issue for starters but also it seems thematically too off to apply to FFXIV. At least with the XI XIII and XV crossovers they're from direct predecessors and sequel. True we have a Nier instance coming but all of that is under SE's control. that and they'll probably give Yoko Taro his own bloody shard of all things just so we can experience the "darkest timeline" all over again!