@Rin_Ayanami For me I usually just go with whatever idea I have no matter how cringy it is (Even after rereading my old drafts I could change it up if I ever want to in the future if I have a better idea) There's no right or wrong when it comes to writing these AUs! I write my fantasy AU with a little inspiration from BSD (Bungou Stray Dogs) and add a bit of ideas of my own, I use c.ai just for a bit of plot ideas incase my mind goes completely blank in a middle of writing. In my opinion, you're free to make the AU any concept you like, for me I made my fantasy AU a mix of BSD inspired and a bit of VnC + my own ideas because it doesn't have to completely be the franchise you're basing it on ^-^ (and you can be creative with the character roles in the AU there are no rules to it)