I know this a bit of a odd suggestion, but I think it might be a rather interesting idea, to say the least.
With the potental that the weather can have in stormreach, why not try something interesting? Once in a while, a monsoon 'season' can affect Stormreach, and when that happens, The Subterrene(And other areas in Stormreach also) can flood with water, thus changing the elements of gameplay(And possibly being able to access areas previously inaccessible!).
Not only would it be an interesting experiment to try with the future underwater fighting update going on, but it would also make playing certain dungeons and raids more interesting, because with new, flooded areas, you gotta rethink your plan, and certain wilderness mobs/bosses may or may not be available as well. I view this as a rather interesting experiment to go alongside underwater action, because it will test a party's reaction to such an incident, and require them to make a decision whether to go through the flooded area, take another route(If applicable), throw water-related buffs, and other choices. Its worth a shot, to say the least.