This is a good example of what I mean. She can stand out, even from under Sakuya's shadow, and her design could easily be updated and fit in the series again. Personally, I would trade out her broadsword for a rapier or epee. Those swords are distinctly Western, and would stand out more in a game or manga from a more generic arming sword or katanas. Dual-wielding could also help establish her more. The fighting style for these swords is different too, with a lot more focus on quick thrusts and parries. Which would make her moves more distinct from Sakuya or Youmu in a manga.
I would also play in a little to her more arrogant demeanor. Confidence is attractive, but taken too far, its a good character trait for a villain to get her comeuppance. She might genuinely be a better swordswoman than Youmu for instance, but her overconfidence could be a severe handicap in a fight narratively. I might also make her prudish or easily flustered when it comes to anything vaguely sexual. Though that might be playing into the fandom meta and Sakuya's knife-garters too much.
How she would play in game, I'm not entirely sure. Her old style is probably not an option, given its similarity to Sakuya's. My first thought is basing her Danmaku on epee and rapier techniques, combined with the aesthetics of Western flowers. But having no experience in bullethells outside of barely beating Cirno and wandering into generic fairy fire out of panic, I can't say that will work.
Since she was a creation of Shinki, she would presumably have some powers, though what those would be I can't guess. I don't think she has any broader abilities laid out in the lore, and her sword summon power is just going to confuse people with Sakuya. My first thought would be opening portals to Makai through certain swordplay techniques, letting her fire at you from unusual angles. You dodge a thrust from her as her sprite clears the map, and a hole opens behind you shooting pellets. You could also make her name literal, and pull the player into hazardous dreamscapes you have to maneuver through.
All in all, she's a good example of why Zun does not recycle old characters. She has some excellent bones, and would be easy to refit in the lore. Her character traits fit nicely, and could be interesting foils to some of the others. But so much of the series has changed since then, that its just easier to make a new character, rather than overhaul one only diehard fans and lore nerds are going to remember. Even if he did reinvent her, she is just going to invite comparisons to the
other maid in the series. :TenshiCry:
