What could we add here from other games?

A transmog/glamour album that unlocks things to use as you obtain the actual item in game or clear specific content.

It might have been declared a logistical or coding nightmare but I feel like all the core starting classes having 2 branches into different roles after 30 like ARC/SMN/SCH would have been to the game's benefit. That style growth can be found in a large number of single player games and also other MMO's

PSO2 NGS character creator/editor. It gives a lot more freedom in the physical dimensions of your character allowing the creation of body types not typically found as player character options in games. The NGS upgrade that came when NGS launched added more slots for decorative accessories and customizations for things like teeth and tongue.

Campaign battles and besieged from FFXI. Campaign battles were open world content where beastmen units would attack outposts in order to claim the region or territory controlling territories offered benefits to players depending on the territories held. Besieged was an event where beastmen armies would actually attack Aht Urgran the main hub area added during it's expansion and it would be on players to assist the NPC's in defending the city. I don't remember the rewards or penalties for winning or losing those events immediately off hand. I found them fun though I know of alot of ppl that complained about besieged being really laggy.