I’m fine with them finishing A Christmas Carol yearly until it’s done, but yes I wouldn’t want FO to be stuck in a rut.
I do think the general “themes” (Spring for a world mythology figure, Fall for classic literary horror/sci-fi/adventure [Halloween], and Winter for winter-holiday/winter themed) are fine for now.
I’d like to see them tackle:
SPRING - Norse mythology (Odin, etc), Hindu mythology (Ganesha, etc), more Egypt (I’d love the Isis/Osiris/Set triad), maybe straying away from “gods” and doing things like the Chinese Jiang-shi (“hopping vampire”) various Greek mythology monsters (MEDUSA), and others. Oh, and Beowulf and GRENDEL.
FALL - well, obviously DRACULA with the same “from the book” ethos they used for Frankenstein’s Monster, the Invisible Man, Queen Tera from Jewel of the Seven Stars (an evil mummy Queen, for those who don’t know, see Hammer Films’ Blood from the Mummy’s Tomb), Deep Ones/“Innsmouth Look” and/or other Lovecraftian human-sized horrors like Pickman’s Model (a ghoul), Erik the Opera Ghost from Phantom of the Opera, Quasimodo the Hunchback of Notre Dame, oh and PLEASE PLEASE PLEASE Countess Mircalla Karnstein aka CARMILLA. And also maybe expand to things like Long John Silver and Martians from War of the Worlds.
WINTER: this is tougher, because there is really only so much “Christmas” they can do and also “Christmas” is kinda limiting and boxed in. That said, they have at least 3 more Christmas Carol characters that are “musts” (Christmas Past, Christmas Yet To Come, and Scrooge himself), and then maybe hit a wintery cryptid like a Yeti?
Which brings me to:
They should have another “slot” specifically for “modern” post-mythological cryptids like Bigfoot, Mothman, chupacabras, grey aliens, Black Eyed Kids, Slenderman, etc. I feel like that’s a BIG missing piece of this line.