YuriChan knows who I'm gonna say, and naturally, she's already said it!
I'd like to see ayu do at least one proper 100% rock album. Just honest, catchy, emotional, raw, powerful music with REAL instrumentation. Well-produced but charmingly rough around the edges. I would LOVE to see Ayu do this. And a collaboration with Tak Matsumoto would be amazing for this.
I also wouldn't mind seeing her collaborate with the guys from Monkey Majik for another sort of approach. Songs like "call" and "Letter" and "count down" and "It was" and "Love song" make me think she could do that pretty well.