I just noticed that water blasting is not available in the powers you can apply to custom AE characters. I hope this gets added at some point in the future.
Edit: I assume that because it was not added on the paragonstudios servers that they may have left no code related to it, nor any instructions, nor comments about how to make it an available selection in AE. I assume this would mean observing how other sets are coded in to the AE custom character builder and attempting to write it in in a similar fashion.
also I assume each power has an Ai attached to it to tell the custom enemy/ally how to use it and whether to attempt move to ranged or melee distance. so the correct Ai would have to be applied to each power in the set. I do know the Ai is not coded to use some powers at all (fields, rez other etc.)
last would be the XP value considerations for water blasting/ water control, those would really be a lot of headwork for the devs to consider. so I understand if this will take a while.