Good question.
As I explained, if we want to destroy the new system project, we simply have to say we'll hold a referendum, then work to counter the idea of the project, generate fear, and say that it will result in a new system, that there will be chaos, and that there will be minority governments and elections each year. We can very easily alarm the public by presenting a situation that should not occur.
So, if the different parties reach a consensus and present a proposal to improve the running of the country, and steer the public in that direction, we could have a referendum. Otherwise, if a group half-heartedly proposes that a referendum must be held, and the day after the release of the committee's report, the parties separate and turn on each other, then money is wasted.