The one thing I would say, is, could this not be down to humans again? If every human had accepted Christ and not rejected Him (remember people rejected him to his face!) if every human had read the Bible and translated it error free, over 2000years, surely the whole planet would have heard the gospel? In fact, I don't know of many people who wouldn't have heard of it, even with history as it is and how it happened, they just choose not to believe because of their culture (man made) or parents (man made). There may be some distant tribes who haven't heard but since apparently all tribes have now been identified, assuming God is real, surely it would have been the Christians duty to take them the gospel? If people haven't due to lack of faith, surely that's down to humans, not God?
Do you think that someone who only had a missionary tell him nth-hand stories about things that happened 2000 years ago has as much of an opportunity to accept Christ as Saul/Paul did?
If each of us doesn't get our own Damascus Road experience - or something equally compelling - then God isn't giving everyone an equal opportunity to accept him.