The RN used to have a more expansive up/out policy than the Army and RAF. The forced retirement option is already in QRs and was regularly exercised at 2-star level and more recently at 1-star level. Unsurprising I know of a couple of guys elect to stay at OF5 and keep a job / pension / CEA rather than take a risky push to star rank. I guess they will just bring the QR forced retirement in at a lower rank and only apply it on those who accept the ToS that goes with a promotion offer.
Of course, the law of unintended consequences will kick-in with a higher rate of promotions to keep the pipe fresh with new blood to replace those dumped-out of the system before their full pension point. Recruitment, training pipeline, retention and appropriate experience levels must just be peachy in the RN to suggest this kind of policy.