Airpolice, it's a tired old subject, but it's still better if people think of it as "aircrew" pay rather than specific "flying" pay. Someone might be in a desk job through no fault of their own and against their will, after all.
Anyway, the rule you mention is already in force. If posted to a non flying-related job, your flying pay freezes, and after 2 years it drops to 50%, then after 3 years it falls to zero.
That strikes me as unpleasant and unfair for someone posted against their will, but at least the main people struck by it will be people who stay away from flying (or flying related) jobs for more than one tour, which is exactly what the blunties seem to want.
Regarding PVRing, you can all take the moral high ground about "retention pay being removed when you're no longer being retained," but the aircrew world is rather unique in that specialist pay ends up as a rather high percentage of total pay. No matter whether it's an allowance or pensionable or not, I'm one of the people who can't afford to take a pay cut of several hundred pounds per month to leave.