I am glad to see you are beginning to warm up to the idea. Agreed, even if this thing makes sense at some point for a display it would be awhile before it is ready for primetime. Maybe never.
These guys may want to turn their entire tank into a skimmer a few hours a day:
http://www.advancedaquarist.com/2002/1/aafeature Those are butt ugly tanks anyway.
I don't see cost being a huge problem since you would be generating bubbles with the same technology as a skimmer? A return pump fed air by a limewood airstone and air pump makes a ton of small bubbles. That brings up the question of optimal bubble size, which could greatly affect cost.