1-Dream Battle maneuvers still work fine against good non-humanoids. Angel hunter go!
2-A Shrine Maiden gets a second school besides Dream Battle, and then her own class abilities also work against everybody.
3-Several Most Dream Battle maneuvers work fine against everybody by default as well. Prayer-Exorcism, Monster Repelling Charm, Fantasy Seal-spread, Monster Buster, Boundary-Duplex Damage Bounded Field, Permanent Border, Fantasy Seal-Fader, Expanding Boundary, Ying-Yang Scattered Spirit, Dream Sign-Evil Sealing Circle, Power Sign-Yin-Yang King, Exorcising Border, Divine Arts-Omnidirectional Demon Binding Circle, Light Spirit-Divine Orbs, Wild Exorcism Dance, Holy Relic-Yin-Yang Sanctifier Orb, 17 out of 35. A Shrine Maiden only knows 13 total at 20th level so there's more than enough leftover to fill that.
3b-All of the above maneuvers still do stuff against goody two-shoes humanoids. Wild Exorcism Dance still ignores DR/hardness and grants boosts to hit. Holy Relic-Yin-Yang Sanctifier Orb still dispels stuff.
So if the party is all goody two shoes humanoids, you could still make a villanous Shrine Maiden focusing on the maneuvers and stances that work equally well against everybody.