You are the head of a development studio that wants to create a proper successor to an online game you loved. What aspects of the original would you keep? What would you modernize to appeal to a new audience? What flaws of the original game would you fix? What new ideas would you realistically
bring to make a bigger, better product, without undermining the spirit of the original? What artistic direction or change of setting might you take? If applicable, would the new game be based on a licensed IP (not the original source IP that you're making a spiritual successor to, which you do not have the rights to)?
For example, if I were to make a spiritual successor to Guild Wars 1...
What I'd prioritize keeping:
Deep skill system utilizing small bar of 8-10 skills with hundreds of skills to choose from.
Horizontal progression through cosmetics and hunting for skills/passives.
Tab target combat.
Enemies using the same skills available to players (though this needs to be balanced independently).
Build respecs being free, convenient, and instant outside of missions.
Fully instanced game design. There's simply challenge types and restrictions that aren't possible in an open world.
What flaws I would fix:
Poor story presentation. Deprioritize cutscenes during missions, prioritizing voiced dialogue during gameplay. When mid-mission cutscenes or visual story segments are required, render characters invulnerable and focus camera as needed.
Lack of interesting gear modifiers. This one needs to be handled in a "plug and play" method that is consistent with the philosophy of free and easy respects. I'd stick to runes that you can freely add and remove, without damaging the weapon or armor. Perhaps even allow you to insert an infinite number of runes in a weapon or armor, while only activating a limited number at once.
What I'd add to the formula
Open patrol zones like those in Marvel Heroes or Destiny.
Passive class trait trees, which are also captured off bosses just like active skills. Would have a more expansive trait tree for your primary class.
Non-human playable races, but they would all use a human frame to share armor skins. Meaning humans, elves/drow, and sidhe would make for ideal candidates.
How I'd change the setting/themes
I'd move from dark age fantasy to a beautiful Italian Renaissance fantasy, emphasizing the art, culture, humanism, and burgeoning innovation of the period.