There's really no "what if" here though.
Danzou and Obito definitively state that Izanagi requires both Senju and Uchiha cells, yet Itachi makes it clear that the Uchiha were able to use and abuse Izanagi to the point Izanami had to be created.
EDIT: I'm pretty sure I said it when the chapter came out, but the whole Izanagi/Izanami history lesson given by Itachi was a pointless retcon by Kishi. Itachi could had easily said Izanami was another Uchiha secret squirrel hax-eyejutsu and everyone would've rolled their eyes just the same.
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