AFPS is only 'big enough' or rather, it's only the size that it is, because of the contracted out element. The argument goes that in the past it has only been as generous as it was because you were contracted out, and that, in theory, if you
weren't contracted out then you would get a larger basic state pension provision and subsequently, a smaller occupational one. I assume that's what you're referring to in your final point and not means testing. But that's another topic..
COPE - pages 10-14 refer:
https://www.gov.uk/government/upload...ned-dwp042.pdf