I've never understood the Ismaili concept of rebirth. Rebirth is a very common concept in Hinduism and it's almost as if we have adopted this..coming back as stones and birds, etc.
From what I can recollect, the Quran is quite clear that when you die, you face judgement. People that have not lived a good life will beg to come back to earth, but this will not be permitted.
Once you die, you face judgement.
That is in the Quran and the muslim belief. Why as Ismaili Muslims, would anyone believe differently?