Michaellll
it feels like revival thing is only good in the hands of villains,bcs they only revive the ones they want as slaves or something like that,and then there isn't really a moral question about reviving ppl :D
Let me explain why the people that were reincarnated so far, were chosen. Rin was a test and Mikoto was a genuis of her own in her time which was why she was bethrothed to the next Uchiha Clan leader to give birth to strong children. Also, Mikoto was needed to heal the bond between her children. Izumi is part of his promise to Itachi so he would be convinced, Shisui was a unit that doesn't need explenation.