Enough about the luggage carriers.
People don't know how to behave. They don't get their own best sometimes. What everyone understands is money - so, nag the airlines to charge for cabin bags but not for hold bags. This will soon ease your trouble as the greens talk louder than any safety briefing ever will.
Medicines can be really time dependant and therefore you might consider allowing a pouch or bag big enough for various medicines. Some medicine, like those containing warfarin, is extremely time dependant and also person dependant. It can be literally life threatening to not take it at the correct time.