WOW... didn't expect the change to DXD but I'm not complaining, grayfia is top waifu of DXD although I'm curious if she will be the only DXD character to join in, i also hope that maybe you include a honkai character though
On the contrary author I like that you change the history of DxD in this FF, because most FF would go directly to the canon route and then remove an already established character in the story just to add in MC's harem.