I personally think it could work as say 2 separate mode where, it's not the genderswaped designs but rather an Incubus curse mode and Succubus curse mode like I said earlier in the thread, with those altered animations for the characters and say an Incubus and/or Succubus (depending on which mode is chosen) that sorta accompanies them throughout the game, with the intro showing the characters getting curse by a group of one or the other, and then which ever character is chosen and the Incubus/Succubus are curious as to what's going on outside the room they were trapped in and go to investigate. Either that or the group of Incubi/Succubi curse them but die right before it finishes and the characters are stuck like that with altered personalities that have slight hints of they're original ones, and then try to figure out what's going on as they're all very confused and lost.
Actually while I'm here, I actually kinda though of another mode that sorta goes along with this one, in that it involve Incubus and Succubus. It's a Succubus mode where the girls get turned into Succubi and Tails is turned in to and Incubus. I kinda felt like it be sort of a complementary mode to, I'll just call them the "Cursed Modes", as well as Evil Mode. With this idea I kinda feel like it could use an idea that I think the og Evil Mode was missing, the characters being able to use their own sex attacks on the enemies. I felt like the og Evil Mode could have used that to show case the characters being corrupted better than them being naked for the entire mode, but I think it would work a bit differently here. I think that the characters would use like a charm attack on the enemies to start up their animations, or have when the enemies are knocked down the characters have time to go up to the enemies and start the animations, or both where depending on how it's triggered could determined which animation plays. When those player initiated animation play in this mode, they would actually heal the player instead of damage them, like how the Succubus heals themself when they attack the player in the main game. You could even have the Succubus and Incubus enemies be unlockable characters for this mode specifically. However since that would be a mode and that would take time to program I think a simpler thing would be to instead of the unique animation have the charm attack so when the enemies hit you it heals you instead. I'm also imagining the enemies do less damage overall, however I do picture the Incubus and Succubus having different animations no matter what, instead of throwing the Incubus rose or the Succubus blowing a kiss at the player, they instead just go up to the play and do their normal animation with that part cut out. Just an idea I had that I felt like sharing.