I think that there should be a limitation to how much diplomacy you can do, because the end result of WoE should be decided primarily by dueling. Perhaps each element can only perform a maximum of 3 diplomatic actions per week?
Also, I propose that when elements enter a trade agreement (or anything including it), a portion of their electrum be locked down, to be returned at its expiry. This would put a premium on fighting with decks which have as low as possible semblance (lower bound=regulations) to each team's base element, so the deckbuilding kind of progresses as the game goes on.