Extra-game purchases really only used for character services.
Previous event rewards returning for the next event with the addition of new items.
3 dungeons a patch / hardmode sequels to leveling dungeons
Explorable building interiors that aren't just used for quests.
Sight seeing log being a scavenger hunt with hints instead of "stand on the glowy thing and /lookout"
Fate chains opening up inacessable parts of the map
8man raids being explorable areas instead of A Square or A Circle or if SE is feeling REALLY adventurous, A Rectangle.
Similarly, branching paths on dungeons with optional side stuff (finding and saving the sex slave prison in sastasha.)
More toned down and practical armor design.
Similarly, more down to earth stories.
The comradere of fate grinding to level up with the entire server in Costa Del Sol, Coerthas, and Northern Thanalan. (yes yes pure nostalgia at this one)