I think you are taking matter too seriously. There is no need to claim which professionals will benefit from GST or not. Overall economy will thrive post GST.
Regarding chartered accountants, they will have huge opportunity under GST.
Scope in compliance management will increase significantly and revenue too will go up.
Existing clients will have to pay more fee and new registration will be at highest rate ever.
You can read opportunities for professional under GST. Not only CA, but every professional whether he is a tax practitioner will have huge opportunities under GST.