A little historical (I mean histerical) perspective on the doctrine:
Charles Russell taught early on that the "little flock" was true believers who were the bride of Christ. They'd be transferred to heaven at the end of the "gentile times" in 1914, when all the earth's rulers are overthrown (p 101 ), clearing the way for God?s kingdom. Mankind on earth would not be destroyed, but serve in a 1000 year "probation" period with a goal of becoming perfect humans like Adam in the garden. Together with Christ, the "little flock" would be come "gods", earth's divine new rulers, serving as "redeemer" and "spirtual mother" for all generations of mankind. They'd be able to appear on earth as invisible spirits or by materializing into physical bodies.
This doctrine was taken straight from Nelson Barbour and some of the other Adventists in the early years.
Russell started linking the 144,000 with the "little flock" and later started writing that the 144,000 in heaven wouldn't ever have to come down to earth after all, because in 1914 Old Testament "ancient worthies" like Abraham, Issac and Jacob were going to be resurrected to earth as perfect humans. They'd be put in charge of mankind (p. 619, 625) and have the ability to receive orders directly from the 144,000, kinda like how perfect Adam communicated with Jehovah in the garden.
After Rutherford took over and dreamed up the "Great Multitude" to populate the earth in 1935, he implemented a harsher view of the big A. Not only will Church and Government institutions be destroyed, but no living person outside of the organization could really expect to be spared from destruction--not even their kids (Riches, Rutherford, 1936, p. 98)...In contrast, Russell had taught that just about all would live to get a chance at redemption in the new system. Kinda makes sense, why join the JWs if it really makes no difference? You'll survive the Big A anyway?