I think I figured that if Sephirot's battle is taking place inside the ARF, all the "water" around his arena was really due to all the Aetherochemical Spills around the ARF. And had nothing to do with Sephirot himself. It's kinda like how Sophia's battle takes place on an Allagan platform and Zurvan's battle starts with him in the Allagan containment facility.

My mind also went immediately to the idea of a bio-dome with the Ein Sof orbs and bio-domes are all about atmosphere control and stuff. And most plants are all about releasing gases (particularly Nitrogen and Oxygen) and pollen into the air for the most part. Sephirot's color scheme also made me think of it. Green is never used to represent water in the elements; it's always used to represent wind/air. Then there was also Sephirot's breath attack. If I were to say Ratzon represented anything, it would be sap dropping down on character.