Honestly, if Lara Croft of all characters is allowed in DbD, I think there's a very strong case to be made justifying Natsuki Subaru's inclusion. Dude is literally perfect for DbD.

>Anime (free money)
>Entire character is based off the concept of trial by fire
>Has a mild cultural legacy (at least in the anime sphere)
>Cosmetic ideas out the ass (more free money)
>Thematically relevant

Just saying