There is absolutely no reason why, given the ventilation and extraction technology which exists today, facilities could not be provided for those who wish to smoke. Strangely enough, most people who smoke have absolutely no desire to inflict it on those who don't. How about a roof garden which requires you to pass through a turnstile magically opened by a £1 coin?
I expect that if BAA felt that they could make money out of a smoking area, they would do it. But unless the entry fee was very high I would guess it would not be economically viable for them to set aside otherwise productive space, install the necessary extractor fans, and install some desperado-proof turnstile system to prevent smokers avoiding the entry fee.
Or are you proposing that non-smokers should subsidise your special needs?