For ships that do allow smoking on the balcony wouldn't it seem logical (and obvious) to have one of those pool side black plastic ashtrays WITH THE TOP ON THEM on EVERY balcony? Smokers would use them and non-smokers could just leave them sit there unused. There was one already on our balcony on the Mariner but I think (?) you normally have to ask for one. They even make them with a bit of sand hidden in the plastic bottom to keep them weighed down.
