So your saying that the element of mobility should have a weakness in what it excels at?
I don't see a reason for airbubble to be so ridiculously weakened. Air doesn't need a weakness in water. There really isn't a reason for it to be so. Not to mention it makes sense airbenders could do this. It's just keeping all the air in one place, and regulating the pressure a bit.
Water technically shouldn't even be able to use water bubble, as they aren't able to adjust and maintain air pressure. Here's why.
Air pressure (airbender's are able to control and toggle this ability passively) deals a big function in this move. If you stretched waters bubble out to much, you would thin the air out due to the atoms rushing to fill vacuums. Changes in pressure can (and I mean easily) turn you inside out. Not to mention the sea level, and water pressure which waterbenders have to keep a conscious effort to maintain or else they'd be crushed under the weight of the BODY OF WATER. Plus, the limited amount of oxygen in each bubble.
Its funny really, saying that an airbender's move that allows them to SHIFT underwater should be nerfed so readily, and by the element of adaptability...
