After fiddling with blades and their affinity!
I found out that it's either impossible or really hard to change their stats as the game auto updates
but if you still wanna changes your stats into something OP(or either just put 255 crit rate and wear avant grande), you can edit a freaking NORMAL BLADE WITH ALL THE OP SKILLS LIKE LIGHTSPEEDFURY(with crit bonus)
and you can actually edit their stat.
edit: BTW this is possible
but need a little bit more fixing as she disappeared after i disengage her
edit: i give up! this game has nasty auto data update that any character with full data is automatically resetted on how it should be