It is definitely fully possible that a way could be found in which a membership could be mutually beneficial. I personally do not think so, but that of course does not mean that it is not possible.

However, regarding smuggling do I wish to clarify that my big worry are ships. If a ship comes to Rotterdam from Amsterdam or if it comes to Rotterdam from Dublin or Porto does not really matter, both are inside the single market so are treated as internal. Everything on board those ships are already assumed to follow the rules of the single market and just a few spot checks are made. However, if it comes to Rotterdam from Montreal so is it checked much more thoroughly, as it is external. If Canada were to become a member of the EU would that change and Montreal would be checked as little as Dublin or Porto, meaning as long as you get something into Canada is it in the EU and will likely not be caught. The only solution would be to keep on treating the ship from Montreal as external, but in that case would Canada already be excluded from one of the biggest benefits of being a member.