is anything in minecraft "really needed"? steambending is already here but in a very very small quantity, + i think the startup for the airbending move tornado pretty much sums up the steamcloud, what you hve to remember about waterbending is its not like the other bending styles (apart from earth in which i mean they both require a source)
it changes ALOT and pretty much anything is possible with it, its a forming substance meaning it can take any shape or form you want it to, its everywhere and in everything even the air in most places... you guys cant expect the developers to cover ALL of these fields but i do think steambending played a big part for waterbenders in tla
i do think the other elements need major developing but i REALLY think you guys should focus on actual water before the sub elements then change the water moves into developed versions of themselves
so lets take water manipulation, you crouch to grab a source then left click to direct it, it can be directed in the air and phasechanged into steam to evporate it, if you lefft click it with phasechange it turns to ice, if you shift it evaporates via steambending..
so now take lets say torrent, add a thing so if torrent is incoming if you left click with waterspout or something it catches the torrent mid air and transfers it into waterwave shooting you in the direction of your mouse.
stuff like this is whats needed, we have everything we need it just needs development and tweaking, maybe a few extra graphic developments to some of the moves and stuff like dual sourcing and so on which im pretty sur you guys are looking into anyway