Always a great topic when this has been discussed. There have been a couple of great threads on this. For pre-war issues I am just not sure there will ever be a consensus even if an appointed and respected group of people laid down the law.
I think Phil has put a great deal of thought into this and is far more of an expert on this than I am but I have a very liberal view on what a rookie card is in the pre-war category. I think it frustrates each of Phil's parameters, in fact.
I am not a rookie card collector but when I am seeking a rookie card it is pretty much the earliest appearance by that player that was intended to be distributed for sale or to advertise or promote the player, a product or the team he played for so that item does not have to be a traditional card but preferably made of paper. Size and population would be irrelevant.