As far as I know, they already use lip syncing features in all their cut scenes. It's not an advanced one, but it still does the job.
You can notice in these two clips from 4.4 MSQ that there are differences in the timing for both the when English and Japanese voice actors are talking. And the lips are moving accordingly. You can also notice there's a part that was said in Japanese, but since it wasn't said in the English version, it was filled with "...." instead if you were using English text and Japanese voices.
https://youtu.be/Nii1n7CHNgc?t=199 (English)
https://youtu.be/Frqy5nGAOKw?t=5267 (Japanese)
The problem is, a majority of the Japanese text can be translated into English without a problem. An example is this dialogue from ARR MSQ with Midgardsormer https://www.reddit.com/r/ffxiv/comme...ersus_english/
And of course we all know Haruchefant's change lol.