I would agree TFF, were they prepared to come out and say that, but that isn't the case. If they said "It's not worth it", they would have to justify risk vs cost.
What the MoD have said is - Not having CWS is not justifiable from a safety standpoint, so we'll bring in CWS......except it's taken them over 18 years to date with no system fitted from a point where it could have taken them 2 years, and they had a working system. This is beyond delays, this is lying, and they should get their balls nailed to the wall for it.
And as DV points out, they are breaking their own rules. Having a safety system and then ignoring it is far worse that having no system at all. It wastes everybody's time at huge expense, gives a false impression of safety, and acts as a block to an effective safety system being introduced.