I'm writing from the other side of the fence, being one of those professional engineers who doesn't hold the CEng title.
From my own workplace, I would estimate that 2-3% of the engineers (not technicians or fitters) hold that title.
I would assume that other aerospace design/manufacturing facilities holding design authority (as we do) are in a similar position.
So "Weeding Out" is not really the correct phrase, "Eliminating Vast Swathes" of the aerospace design profession would be closer to the truth.
In my case, I feel no particular urge to pay £140 pa for a magazine that I do not read. Can you persuade me that the RAeS offers any more than that?