The background thing almost feels like a moot point now. 2 taoists, 2 bhudists, 2 moriyans, Reimu, and Marisa is already 8 characters. And then there's a last boss (and maaaaybe mid-boss, but only maybe.) It'd be really hard to expect much more than that given that Tasofro is making everything from the ground up.
I didn't realize it before, but now with the likelihood of 2 Moriyans being here (since everyone else related to the religious factions is in the background already. ...yes, I know I just said the background thing almost feels like a moot point now. Whatever), Kanako really should be there (2 Moriyans means there's room for her after the obvious Sanae). After all, she, Byakuren, and Miko were the three "head honchos" in SoPM, and since SoPM was almost like a prelude to HM, it would make sense for Kanako to be there when Miko and Byakuren already are. And like stated earlier, Kanako really has been explicitly stated to be the one responsible for going out there, putting on a show, and gathering faith, which is what Hopeless Masquerade IS. The entire point of the whole story is to go out, put on a show, and gather faith, and that's what's Kanako's job description has been ever since Suwako stated it back in MoF.