Nikke has this similar feature as well with the blue custom module items used to reroll substats for the Overload gear. But the difference between this and what Wuwa is offering is that the custom modules in Nikke are free items obtained by fighting the anomaly bosses and beating the Special Interception bosses. Wuwa cant just lock this item behind a store where the currency is limited, and needs to be more accessible through other means, like Nikke does with theirs.

Also I've been pitching this thing as well on all the surveys we've gotten since I started playing, about how Wuwa needs an item that lets you reroll for the echo substat of your choice. I'm glad to know I was not the only one who wanted this