I don't see a provision excluding fiscal issues from going to a referendum?
My intention was to leave the door open for the ways that citizens can influence policy. However, the guardrail of a two-thirds vote in the Senate is there to ensure enough consensus for what is deemed reasonable to move forward with. There's also the matter of whether the majority of the nation will agree to whatever propositions are approved by the Senate. In that sense, fiscal issues would receive scrutiny from far more people than just, say, eighteen Senators and one President.