HIKARU_GENJI
Just a what if scenario. What if instead of meeting Isshin when she sensed the Hollow, Masaki met Gojo who was on a mission. Which made her feel curious about him. From that day on, they would start seeing each other. Making her fall in love with Gojo. And then this will affect the future because Ichigo will never be born. Just a food for thought. No need to mind me.
Really, the entire idea of Substitute Soul Reapers isn't a bad idea on its own, but for it to function reliably and with minimal long term problems, they would need to create a 14th Squad located in the living world. Something similar to what Uryu's grandfather proposed, a first responder squad fo immediate issue.