To me, Kurumi represents a character that has a lot going for them in terms of possible stories to tell with, over being some significant player in Gensokyo politics.
Kurumi is another PC98 character that has nothing special.
She's one of two gatekeepers (a first in this series), in which her "gate" is the Lake of Blood that gets drained. Kurumi and Elly inherently have a connection to Yuuka, who escaped PC-98 hell to become a minor character in Windows. I'd also say having another vampire outside of the two everyone knows about is a bonus.
I don't really care for the notion that a character needs to be intimately involved with the narrative of a Touhou game or print work to be interesting. This just leads to most fans making content centered around the same characters over and over, ignoring everything else on the table because any relatively unpopular minor character gets the reception of "Literally who?". It just takes some creativity and knowledge on what the character's traits are (you can get an idea on a PC-98 character's personality by reading
how they talk and interact), and from there you start crafting a story. It doesn't have to be grand, it only has to matter to the character involved.
You can have a story where Kurumi, Elly, and Yuuka catch up on each other's lives and hang out, maybe a story where she interacts with the other vampires. Heck, you could even think so far outside the box and pair Kurumi with Rumia. They are both Youkai associated with darkness, vampires don't like sunlight, Rumia can cast a darkness bubble, and they both seem to be mischievous. It can make for a unique plot, where they are covering for each other's weakness during the day and bonding over antics.
