Try_hard
Author, in my opinion, this is a bad move. Unless you greatly alter their own world, it would be dumb if they experience the same hardship they went through. For example, Rias, if she can't capitalize on the gift given to her and went through the same events as in canon, then it is not their fault, it is your fault as that would simply be copy-pasting with an extra character which is hardly considered a fanfic but plagiarism.