1.) A lot of people who've never engaged in underwater hunting will be killing lionfish, possibly a few per dive.
True. This is happening now. This past dive season I saw many dead Lionfish brought back on board.
2.) These people won't be expecting or experienced in dealing with sharks.
I think this is mostly true. Although sharks are sited occasionally I do not personally know any "everyday" type divers experienced in "dealing" with sharks, so to speak. Divers that are "not beginners" usually have some knowledge about how to behave when a shark is present but I do not feel most have experience in dealing with sharks. Those with experience in dealing with sharks would be the "shark handlers" seen on "shark dives"
3.) Some say sharks are fairly bright; some may learn divers leave wounded or dead lionfish floating around.
True
Do you figure this is just hypothetical crap that won't amount to squat in the real world, or do divers need to be mindful of sharks if they start killing lionfish?
I do not think it is a concern. The reason being is sharks typically have eating patterns. They know where to find food and I suspect they usually repeat the same successful patterns. Also, I am not seeing the dead Lionfish being left behind.
This is an interesting point. In Alaska and some areas in Canada the Grizzlies have adapted their successful patterns. During Moose season, after a rifle shot is fired, it is not uncommon to have a grizzly wander in. A couple of years ago, one literally came over a hill to find us. He sat a couple hundred yards away until we gutted the moose and left. Gut-pile dinner with no effort. We often underestimate the intelligence of other animals in our kingdom.
The big difference is the grizzlies already like the gut-piles. We have to figure out how to get the grouper and sharks to acquire the taste of lionfish.