It should simply be illegal to change the conditions of support and pension to something other than what was agreed to at the time of signing the contract. And if conditions change, the take effect after that contract is fulfilled, and the previous conditions are effective for that period of employment.
You know, just like everyone else.
Unfortunately because of the unsustainable effects of defined benefit versus defined contribution plans, that is an impossibility and politicians who didn’t know much about economics are the parties to blame, but change they must or the result will be far worse. After total collapse or bankruptcy what will remain is NO benefit.