CW: Talks about character concept art leaks.
Coppelius sure is suspicious
Reposting with edits for clarity, context, and brevity from the original post at https://www.reddit.com/r/Genshin_Impact_Leaks/s/MjFQNX1qaA. This was written during 4.6, before 4.7, and before Emilie's character design was revealed.
The following is regarding a leaked character concept art, in response to the thought that the character can be considered scrapped if they don't show up by the end of 5.X (Natlan). The character has been nicknamed "musketeer guy" (by the original leaker of the concept art) or alternately, "musician guy."
My theory—assuming this concept hasn't been scrapped—is that this character concept could be for someone related to Coppelius, the Fontanian playwright active 500 years before the present events in Genshin Impact.
(Spoiler) The concept arts in question
Image: Unreleased concept art
If this character ends up related to Coppelius (or Goldoni I guess) I'm actually starting to think he might be a Snezhnaya-era (6.X) release (assuming he's playable).
Could he have been scrapped due to a scheduling conflict?
It could be they couldn't fit him into the Fontaine schedule and scrapped him: He seems to have a lot of Remuria/Petrichor theming, but 4.6+ (that is, the region he'd fit the most design-wise) is stacked with AQ characters (Arlecchino, Clorinde, and Sigewinne). Also, if his color scheme is any indicator of his element (making him dendro), and if we assume they wanted a dendro release going into Natlan, they might've picked Emilie over him (assuming she's actually dendro—but I think she might be; Chevreuse or Chiori name-dropped her during Fontinalia and talked about her expertise with flowers). (Or he might be anemo thanks to the light teal in his design, and the bird, and the trumpet, and the musical motifs....).
Note, however, that the recent characters have had really strong story releases (Xianyun's SQ matches the theme of family during Lantern Rite; Chiori during Fontinalia hinted about her SQ's Fashion Week; Clorinde is releasing after Remuria, so we can get some background on the Maréchaussée Hunters before we jump into her SQ).
So it could be that there isn't enough story support to introduce him yet, to tell the story they want with him. Delaying him into Snezhnaya would give them time to set up the background for him, and give the players time to get through all the supporting material before they release him.
Coppelius, Snezhnaya, "this guy," and love.
Then, consider that Coppelius was "obsessed with love." "Musketeer guy" may end up related to Coppelius based on the themes in his design heart motif (red, complementary to green, making his heart brooch stand out) musical motif (conductor's baton in one; trumpet in the other two) * art nouveau/Petrichor-related designs (Petrichor is where Coppelius' descendent Goldoni hangs out)
Love may or may not end up a theme of 6.X (Travails Trailer), but if it is, "musketeer guy" could fit nicely into that theme—either as a descendant of Coppelius or just based on the heart in his design—and could end up a late Fontaine release in Snezhnaya, the way Chiori is an Inazuman character in Fontaine.
Art forms; Coppelius and the arts; "Golden Hyperborea"
Additional speculation: Each region has an art form related to it. Mondstadt has poetry; Sumeru has (oppressed) dance; Fontaine has its operas and plays/movies; I'm hoping Snezhnaya may have ballet (please!) or figure skating. Basically, there's still room for an art-focused character like "musketeer guy" ("musician guy") to crop up in Snezhnaya, even if he isn't related to the Fatui. I can even go further and say that the fabric store in Inazuma was setup for Chiori in Fontaine, so all this setup for Coppelius in Fontaine could very well be setup for "musketeer guy" in Snezhnaya (otherwise, why would Mihoyo bother having a playwright like Coppelius at all, or add a living descendant like Goldoni, just to remind you Coppelius existed and had descendants.).
Coppelius himself as a historical figure in Fontaine is also incredibly suspicious if he's the "opera-writer" mentioned in Flowers for Princess Fischl, who was (if I'm interpreting it correctly), almost chosen to be Hydro Archon over Foçalors "the philosopher/Zarathustra[1]." Maybe when (if) we get Furina SQ2, if that plot thread wasn't scrapped (I mean, the "Reman Republic" made it in as Remuria, so...). The 4.0 Fontaine craftable catalyst, Flowing Purity, reports that Coppelius died; and then, fast forward to 4.6, we get Goldoni walking around confirming that Coppelius had descendants. One of Coppelius' plays is definitely related to Snezhnaya as well: "Golden Hyperborea." I find it all very suspicious. Even if "musketeer guy" doesn't end up blood-related to Coppelius (or is Coppelius himself, e.g. in a flashback/NPC cutscene) I'd be very surprised if he ends up not related to Coppelius at all.
[1] Zarathustra, who declares "God is dead"; Carlo Goldoni - Italian playwright and librettist; Dr. Coppelius: from Coppelia or The Sandman*, who made a life-sized dancing doll (Coppelia or Olimpia)
Relevant Excerpts
"Flowers for Princess Fischl"
Beast of the World: Gesamtkunstwerk
In certain probabilities, this is the Beast of the World that the Immernachtreich would be faced with in this cycle. Its battle strength is around thirty.
In a distant causality, if the philosopher Zarathustra was not chosen, then the opera writer would have gained victory in the contest over the will of the world.
Once Gesamtkunstwerk takes the stage in the opera theater of the apocalypse, many more Beasts of the World that reside within the center of the universe will inexorably begin to appear as well.
In the final volume, the weakness of the Beast of the World: Saint of Seven Tears (whose combat strength was ten, and therefore equal to Fischl) was quite out of the ordinary, and the Saint merely wept for Zarathustra at first, a choice that seems undeserving of any blame.
Both Zarathustra and The Musician exist to give praise unto the Prinzessin der Vererteilung. One proclaims the agony she suffers in her heart, while the other proclaims the grandeur of her travails. The Prinzessin, of course, will not favor the latter, for of such things would she be ashamed.
Mitternachts Waltz
In their long journey across space and time, the Prinzessin der Verurteilung and her Night-Severing Raven bore witness to countless stories and their endings, each a raindrop that flows at the journey's end into a bitter sea. Every young man's rage at injustice must turn to calm. Every passion must be ground into dust by the march of time, before being turned to wild paranoia upon that inverted, ancient tree. Even the branch of the tree of time upon which the great and glorious Reman Republic nested would be cut off in the end, such that the nation founded by the other twin child of the wolves might rule.
Final Thoughts
I'd say I'm really just obsessed with Coppelius... his placement in the lore is extremely suspicious, and musketeer guy being playable and related to Coppelius would be amazing (if it happens) because of all the implications of being playable (SQ or hangouts, weapon lore, etc; anything leading to more information about him).
Other Thoughts
It's weird that Fontaine (with all of its musical themes) doesn't have a musician character. (The others are Barbara, Xinyan, and Yun Jin; Furina if you count singing, but her theme is more for acting/directing now that she's retired from the stage).
He's got a playable design: the cape in the back has openings for movement, and he has enough going on in the front to make for an interesting model. He's got a number of good motifs: birds or bird wings on his shoulders, plus the bird and feather on his hat; the heart brooch at his neck and on his bird, and heart-shaped jacket lapels; checkerboard pattern and gear patterns of Fontaine; smooth swirls. There's two versions of the monochrome one: one with a symmetrical garland/scarf and one with an asymmetrical one.
Teal (and the horn and bird) might indicate anemo actually, rather than dendro.