I'm pretty sure Byakuren will be playable in the full release. From the game's opening movie (translation copied from the Touhou Wiki):
But in Gensokyo, there were the religious
whose occupations were to satisfy the hearts that had been lost.
The monk who has built a temple in Gensokyo
The Taoist who abandoned the material world and aims for immortality
And the shrine maiden who seeks reinstatement.
I'm 99.9% certain the monk in question is Byakuren and the Taoist in question is Toyosatomimi no Miko. The shrine maiden in question is, of course, Reimu.
But in Gensokyo, there were the religious
whose occupations were to satisfy the hearts that had been lost.
The monk who has built a temple in Gensokyo
The Taoist who abandoned the material world and aims for immortality
And the shrine maiden who seeks reinstatement.
I'm 99.9% certain the monk in question is Byakuren and the Taoist in question is Toyosatomimi no Miko. The shrine maiden in question is, of course, Reimu.