Given that they summon units from the rivers instead of producing them, will the river zora have access to naval units?
Also, may I suggest a zola-equivalent to the goron bomb throwers? In this case instead of throwing bomb flowers they instead throw, or rather toss, live bombfish at their enemies.
On a different note, I found some rather interesting concept art for the Twilight Princess zoras. Apparently they were going for a more "realistic" appearance from what I can tell, but I noticed that the design on the right bore the coloration and similar head-fins of the river zoras of earlier games. Perhaps the designers had intended to make a halfway point between river and sea zoras?