Biggus, I see what you're saying but you can't really, can you?
If you reduced Spec Pay the instant you awarded it then no-one would ever get the full whack, in which case they would have been recruited on a bare-faced lie, a ruse!
The SP's done its job once recruited, and continues to do so until PVR, at which point no amount of 'recruit and retain' pay can make a difference. I think the two (recruit & retain) are surely intrinsically linked.
As for cutting all pay - if it wouldn't create a management nightmare, which it would, i'm sure the powers that be would love to let all PVRs go instantly. Then they would stop all pay as they'd be out