Another playable character huh? In Touhou for the most part the playable characters are generally seen as the main cast, and even then those who do pop up as playable occasionally need a storey that ties into the incident. With that in mind I can only think of a few characters.
Kazami Yuuka – Yuuka was playable back in Mystic Square for the PC98 era and Phantasmagoria of Flower View. In PoFV I generally don’t see it as a major game as it seemed like an experiment into split screen co-op gameplay as there’s quite a lot of playable characters for that game.
Alice Margatroid – Alice is included numerous times throughout the Touhou series, but she’s only a playable character in the fighting games.
Yakumo Yukari – The gap ha… I mean the Youkai of boundaries. Although come to think of it, a game where you play as Ran would probably suit better as Yukari could command Ran from behind the scenes without bothering to leave home, which sounds more likely. Actually I quite like that idea, Yakumo Ran it is! A true boundary team!