While I am very in favor of the recent change to Banishment that makes it only works on hostiles, I wanna propose a slightly further change that I feel would make the spell a lot more fun and lore accurate:
Banishment should be modified to send player characters, specifically Aasimar and Tieflings to their lawful-alignment/Racial plane. So when banishment is used on either an Aasimar or Tiefling character they would be sent...
Lawful/Aasimar: Celestia
Neutral/Aasmiar: Elysium
Chaotic/Aasimar: Arborea
Lawful/Tiefling: Dis
Neutral/Tiefling: Hades
Chaotic/Tiefling: The Abyss
With the concept being that, no matter the characters Moral Alignment (Good->evil), racially, they will always be from either the good(Aasimar) or evil(Tiefling) planes, the rest would be determined by the specific characters Lawful Alignment. As for the rest of the server, it would be fairly self explainatory, Fey would be sent to the fey-wild, Shadowvar to the Shadowvar, Genasi to their elemental planes, and all creatures from the native plane who are hit by the spell in another plane? Back to the Material Plane.
Each plane would need to have a PvE safe area in order to accomodate lower level characters and prevent them from being killed upon arrival, and I also believe some of these planes don't presently exist on the server (Though I could be wrong). So this would likely require some amount of map creation effort on top of the changing of the spell, but even small themed areas with not much in them would serve to be far more interesting and lore-accurate than the present situation where Banishment is a more effective instant-Death spell than a Palmasters Death touch (Versus outsiders). As a plus, if any new planes are created, at least from there contributors and DMs would have areas upon which to expand the story of Arelith.
(Also as an aside, if this does get implemented you should be able to directly target your ally's to forcefully send them to their native plane. It would make for fun times between friends, or maybe even a quick escape from other planes)