While a community editor would work fine I think a official one would have a crucial advantage. Firstly like the faction creator it could be accessible from in game, and that would really shove it in peoples faces. This is important because the easier it is for people to notice and use the more people will use it. I mean after playing a game or two of elemental who wouldn't want to churn out a few custom quests before starting another game.
I could dedicate a few days to learn how to make proper quests through xml but that's not the point. It's all about getting as big as a community as possible producing and sharing quests, and people are lazy. You don't have to lurk the forums to learn about and use a official quest editor. It can be advertised in-game.
You could have basically every single player messing around with the editor between games and it would add so much to the game. Repetitive quests make the game boring fast. Also after using the editor what are they going to do next? They are going to head to the forums and download community quest packs, and after that they are going to get involved with other areas of modding and the forums. Thus the population of the forums and the community profits as well.
A good official quest editor would improve the game and community 100x, no joke.