I'm most likely late to this thread, but I really wanted to do this too (and get a contribution in-game as well), so I did some! 2nd Encore has more potential slots, though, so these will probably go there instead (unless SGM pulls out more slots)! Anyways, here they are!

1. Shiki Ryougi and a regular White Bunny Sagan (Kara no Kyoukai)

2. Jolyne Kujo and Stone Free Sagan (JoJo's Bizarre Adventure: Part 6 - Stone Ocean)

3. Jean Pierre Polnareff and Silver Chariot Requiem Sagan (JoJo's Bizarre Adventure: Part 5 - Golden Wind)
[This was inspired by a comment in an Annie color palette thread in r/Skullgirls, forgot who exactly, but your idea is now eternalized! I'd also wanna thank them for inspiring me to do the Jolyne Annie above!]

4. Linne and Kuu Sagan (Under Night In-Birth series)

5. Nanase (Under Night In-Birth series)

6. Hiyori Asahina and Sagan as Hibiya's Hiyori doll w/ her sword being in the colors of "Kagerou Daze" (Kagerou Project)

7. Soji Mitsuka [Female] and the Male Counterpart as Sagan (Gonna Be the Twin-Tail!!)
EDIT: I did more!

8. Marie and Velvet Room Sagan (Persona 4: Golden)

9. Momo Kisaragi and Sagan as Shintaro Kisaragi (Kagerou Project)

10. Hibiya Amamiya and Hiyori Doll Sagan [sword colors are switched around to parallel Hiyori Annie] (Kagerou Project)