Just an idea I've decided to work on for now.
Imagine an MMO VN, (massively multiplayer visual novel), where you play as a character. A quiz is taken after you decide on a character, to see if you really know enough to take on her role. (Storytelling and stage skills, as well as considerable knowledge of Touhou is a must!) Characters to play are ranked by difficulty - for example, Marisa would be "Hard" because it takes work to mimic her mocking and funny character.
The player does not walk around in a bird's eye map and fight monsters to get exp, like an RPG. A "room" is just represented by a panorama image, where certain events can be triggered by clicking certain parts of the room (think Professor Layton).
To prevent this from becoming one messy chat room, the max number of players in a room is capped, and conversation is one-on-one only (unless two+ characters form a "party"). Sprites with different emotions are used (similar to the canon games)
Basically, it's an attempt at bringing Gensokyo to life. More stuff can be added later on, but I just wanted to lay down the fundamentals. Music, sounds, and graphics will be from non-canon sources (according to ZUN's legal terms).
Major work will be required for the sprites and panoramas, a little less work in programming (I'm a computer science major and I think I have this covered) but overall I think it's doable.
My concern would be low player turnout. Would anyone be interested in playing? Why, or why not? Suggestions welcome. Helping hands may be considered.