Crab
I think 140kt plus for an upgraded SK is somewhat optimistic despite what Mr. Carson might say! Even if it were possible, the long term implications of fatigue on an already ageing and worn airframe would preclude it being a sensible option. I think it's (nearly) time to let the old girl go and embrace some more modern technology. Aircraft replacement is an emotive subject and, very rarely, is the replacement embraced. That said, I'm pretty sure that whatever type (or types!) appear on our shores in the near future will be a step forward in terms of performance/capability.