I remember a translated interview talking about when viera were 1st being added; they originally were going to do 1 or 2 ear types to allow for more *options*? (idk if that was the correct translation) and viera were supposed to have the two different looking races apart from being bunnies- the Rava were meant to have the upright ears just like Fran. And the Veena were supposed to be shorter, with cuter features and lop ears but they decided against it, either bc of time restraint (they literally could have waited for endwalker to release a finished raced instead of a rushed one)
But frans ears don't move and I believe they used her model to port some viera stuff.

Unfortunately, ear movement will most likely never happen - it's probably something that should have been programmed into the viera before they were released. Or might have been possible had they had less ear customization and only 1 ear type (like the miqote) Had the viera actually looked like the ones from ff12 (they all had close together, forward sitting upright ears which I still wish we had had instead of what we got...)