As we have seen in ARR, areas are much more alive and realistics, full of animations just a real ecosystem of flora and fauna.
The only thing missing to make it more real is seeing monsters fighting each other, it was the case in FFXII and FFXIII where you could find fights between monsters.
This is only a visual aspect and should not necessarily affect the gameplay, for example: the monsters could fight each other, damaging them self or not, and when you have to fight them engagements with both is mandatory.
Or another example: the monster can first help to defeat his opponent and then fight you, possibilities are limitless, and could involve beastman's tribes fighting each other ect.. but this is not the focus.
I don’t know if this would heavily affect the servers and slow down their performance, however, this is just an idea.
Comment please! : D