As mentioned elsewhere in the thread - that's not gonna happen, unless you are daft enough to smoke in your seats. The stewards have very limited powers. You aren't obliged to provide them with ID or identify yourself to them. They're often students on minimum wage. People will just tell them to fuck off. There are no coppers in the ground any more, and even if there were they wouldn't intervene.
I can happily go without a fag for two hours, and sure smoking's harmful but the principle isn't related to this and it is important. We've known smoking's harmful for about 60 years now, and have banned it in indoor public places. Fine. But it's still perfectly legal outdoors and about one in five of us smokes. Most smokers are considerate. We're not talking about smoking in the Family Stand toilets, we're talking about smoking at the bottom of the kop steps, in the open air, well away from the seats. With thousands milling about.
For well over 100 years it's been a Bramall Lane tradition for fans to congregate below the kop and enjoy a drink and those who smoke, a fag. The PL doesn't own the club. The spiritual owners of the Kop are the Sheffield fans, the Shoreham Boys, who have been supporting this club through thick and thin, for generation after generation.
Smoking below the kop steps will only end if the majority of the kop finds it unacceptable. Not when the PL tells us.