I am better able to answer your question now. I misinterpreted what you meant at first.
There are two components. The CLC's proposal to double the CPP and the proposal to guarantee the CPP.
But I think you are referring more specifically to the current pension plan. It offers no guarantee, and the only way to get one is to pay for it. A mechanism for that does exist. When you contribute to a pension plan through an insurance company, that company can fully guarantee your pension for a very high price.
A separate guaranteed fund is just part of the solution. There have been instances where guaranteed funds were exhausted because losses outweighed what was in the fund. If you want a full guarantee, you have to go through an insurance company, and that costs a lot more, of course.