I think the right 30-sec movie, in the safety briefing, might convince most people of the folly of grabbing carry-on.
One problem is what to do when there is no means of showing the film on board? I've just come back from a round trip to Manaus and there is no a/v system of any kind on the airline I flew. I'm sure they are not the only low cost (high fares though !!) carrier that doesn't have IFE.