I am a scuba junkie. I dive at every available opportunity. As a matter of fact the single biggest conflict with our ShadowRunning is my diving.
That aside... I would gladly pay a heck of a lot more for a scuba tank if it could fill itself - No compressor needed. The compressor is built into the valve. Obviously this wouldn't work for anything but air... i.e. no nitrox, no trimix, no pure oxygen for decompression.
As the gear descriptions are pretty minimalistic in some cases, and the state of the art in many things, is quite a bit beyond 2004, it may not be unreasonable to belive a 2063 scuba tank can fill itself without an external compressor.
Taking this one step further, to make an exotic diving gas - nitrox, trimix, O2, etc. One would only have to connect the tanks valve to the cylinder holding the gas. There could be a nice friendly user interface allowing you to select a breathing mixture and a prompt to let you know when to change source cylinders.
Granted 3000 would be a bit much. In today dollars, that would buy a whole compressor, a few cascade bottles, and a couple of tanks to dive with.
Just thought I would post an alternative notion...
--Dave