Hmmm.... I would have....
I would have some sort of versatile magic power based on the western elements. (Not the eastern/ Wu Xing ones, like a certain asthmatic purple girl)
I'm pretty sure none of the Touhou characters have that power, since all the magic ones other than patchouli seem to dedicate themselves to a certain type of magic (Alice with dolls, Marisa with light)
Generally, I see the western elements as: Fire, Water, Air, Earth and Spirit... While they do seem quite similar to the eastern ones, they are rooted in different history. Such history being the greeks!
The interactions between the element of "spirit" and Gensokyo interest me, would it be spirits in the sense of departed souls? Maybe harnessing their power? Who knows! This is an amazing thought experiment! Thank you for asking!