GACKT - he would make up something epic...especially talking about intrumentals and lyrics
Alex Band - light, melodic rock
Amy Lee - new genre of music that I don't even know now xD she's still silent about the new album, can't say what she's composing but I bet it would fit Ayu.
MIYAVI anyone? xD can you imagine how awesomely crazy would that be?? XD
As for lyrics I want CREA/Ayu she's poetic enought to write lyrics for herself, besides I love them!