That is a very good theory and I am openminded on all aspects of Spiritualism as Know Earthy being has the TRUE answers.
But what if we have free will to grow Spiritually when we pass, we certainly have free will on the Earth Plane, if we have free will it is then our Spirit that then decides when to progress and if that is by means of Reincarnation so be it, but we surely all have free will to chose what we do.
I agree with Sandysmiles we are here to experience and for Soul Growth, we are all connected to the same force of life and no one is any better or worse than the other, it is just what that person has chose to experience.
On the Earth plane it happens, one person might want all the Spiritually fruits of life(healer, medium etc) and will work so hard to get it, the other person might not want that, who is better???(none)
Life is an experience and my personal view is that as on the Earth Plane, so also in Spirit do we make our own decisions and when the time is right for our Spirit, it will decide to advance itself in whatever means it needs, but it is at its own freewill..