That will be quite a case to argue and prove intent to harm when a person willingly purchased a product that may or may not be safe to ingest, that a store put on the shelf with no knowledge or intent to cause harm, and to prove that the use of the product was not a direct result of misuse by the consumer. I could go on all day but I think you see the point. Also the points your making about mixing are valid because no one is overseeing anything.
Who's to say that if a consumer buys a 6mg nic bottle however suppose that batch wasn't mixed correctly but instead was made with 100mg nic in the 30ml bottle and was imported from another country and caused illness or death to a consumer who relied on the product he bought to be safe. Are we then going to tell him to go hunt down the manufacturer and bring suit against them when you purchased a unregulated product without being aware of the possible risks because someone told you its a solution or safe alternative. I think most of you can see the problems here and understand that while this exact scenario isn't actual it could be.
Actually in the previous examples you have used numerous times in this thread it would be very easy to prove that. You keep moving the goal posts.