Things to add could be new mining areas, and I personally really agree with a suggestion made by user "Immagetchyah" with the gen 4 underground mine. I also would really like to see quests, though more linear quests than a simple "Go there" or "Do that" type of deal, something that rewards you for making you think rather than just being told exactly what to do, whether it's different endings (With a rule to prevent spoilers for those that haven't done it), a long line of quests with individual rewards, a boss battle etc, just something that would spice things up, and ideally for longer periods of time like dex or gym, but is less grind mandatory or time dependant (With finding each pokemon for dex, grinding up a gym team and waiting for a leader being the examples of what we have now)