An additional problem is what happens when you need to patch the game? If you need to modify some form of quest or dialogue script written as a coroutine, how d

An additional problem is what happens when you need to patch the game? If you need to modify some form of quest or dialogue script written as a coroutine, how do you migrate the state? What if you've changed the script 5 times in a series of patches, and the user is still on version X? Then again you still have this problem even if you power your quest/dialog with data instead. Without sufficient information it's practically impossible to make a smooth migration.