The Subjunctive Mood

I ran against a sentence in Longman Grammar Exercise Book illustrating the use of the subjunctive mood (2), which is unreal condition at present. It said, "If I were the Queen of Sheba, you would be King Solomon." (Probably, a talk between children). First, it seemed to be a perfect sentence, but then I was wondering whether it is grammatically correct because it refers to people already dead, that is to people who cannot be viewed as existing at present. So, wouldn't it be more correct, albeit clumsy, to say, "If I had been the Queen of Sheba, you would have been King Solomon?" In more general terms, would it be grammatically correct to say, for example, "If I were Uncle Jack, I would do this and that" if Uncle Jack is a deceased person?