Honestly I wonder if a solo career is even what Aya wants (in terms of music). I have the impression that if she really wanted to continue releasing singles/albums she would have been given something by now (am I wrong to assume she has some control over her career? If you think about it, GAM pushed for an album/tour and they got it.. I really doubt that UFA would deny Aya new material if that's what she was really aiming for).
I think in some ways, GAM is doing the opposite of ruining Aya's music career- if it weren't for the unit, would we even be hearing from her (music wise)?