>>3802816
Another thought:
If the Xenogears team grafted an abandoned plot thread from Xenogears into FF8, then what might that have been?

In Xenogears, we know Id destroyed Elru, and the only survivors were Ramsus and Domina. Data miners have found that Domina was potentially a playable character at some point in development. Domina is a female, which means she was a potential host for "Mother".