Interesting...though I'm not sure how a crossover between the serious X series and the goofy touhou series would work out.
Touhou is only goofy if you're going by fanon. Otherwise it's actually got a lot of dark and creepy undertones, particularly off-screen.
Anywho, I'm not really into RPGs but I'm rather intrigued by how this'll go. I agree on the bit with the rooms and such.
Is Reimu, Marisa or any other human characters in it though? In theory they'd be the only ones that aren't around by 21XX if Gensokyo existed in the MMX Universe.