RebDoniel, any time you change a rule there will be a balooning effect right away. In order to really know how things work you have to study a place that had such laws in place for a while.
While smoking is not healthy and is irresponsible, the effect is long term and down the road. You can’t compare a smoker to someone taking illegal substances. As far as I know, BH Yeshivos do not have this problem.
Like everything else, who knows what the future holds and what a Mussar Shmuess will sound like a couple of years down the line. But sofar, it is not an issue and please don’t make believe it is. People take the word of fiction seriously, even while being aware that it is fiction.
Maybe, if your story would be about a Bachur hiding his regular nicotine sigarette, that would help implant the idea that it is not normal to smoke. Think like a journalist: how you can change the world with slight inferences and biases.