This is what a professional editor from another forum had to say about the original question on this thread;
The subjunctive is complex and very useful. \"If one were to..\" is not subjunctive; it's conditional. If i were you, i'd learn the subjuncive well. If one were to know it well, he could do great things with the language. I'll tell you more soon. Must run. Today i can give you a better explanation.
He was a bit rushed in writing this message, obviously, but it seems that 'were' is the correct word. But, this person I quoted may have some sort of irregularities to tell of, who knows? But for now, it seems that Pravit's question has been answered; 'were' is correct.