I can recall reading about a life saved by BC rebreathing ... it was on a commercial dive, someplace tropical and shallow (Bahamas?); the diver was working solo and got pinned somehow under some big heavy stuff (pipe?) and rebreathed for over an hour - - in/out of his BC for awhile, then dumping & refilling, etc - - before his coworkers realized that he had disappeared and started a search, finding & rescuing him.
What audience is a great question.
Probably what most audiences of basic divers would be surprised at is just how crude ... and simple ... BCs were ~30 years ago. And yet we survived and had fun.
And in a similar vein of the question of 'travel' BCDs, at lot of the modern stuff has gotten overly complex and .. call it "overbuilt": what would be a good illustration for an audience "Hands On" would be to get an old BC and a brand new one and show how thin the old stuff was ... and yet it still lasted for years. Unfortunately, the old lightweight stuff isn't around much anymore: all BCs are typically 1000 denier nylon to make them big, bulky, heavy and not particularly inexpensive -or- travel-friendly...and instead of offering a not-overbuilt BC, the market is trying to sell us a second BC just for tropical travel, rather than to, heaven forbid! use lighter weight material that's only going to last for a mere 20 years/1000 dives.
-hh