Weekly quests have been brought up before, and generally have had good responses.
Personally I prefer the idea of weekly quests over daily, because they can be more difficult and we already have the oracle to encourage people to come back.
To me, the reward of a free upgrade or rare weapon seems too much for something like EM an AI3 or AI5, however, they should remain balanced for the new players. If there is a way of scaling the challenge (but not the rewards) it would help all players, while lessening the gap between the pros and the noobs rookies.
But I am very much in agreement that more quests, whether daily/weekly/annualy would be a step in the right direction for Elements.