Why can't the "details" be worked out before we vote? Are we voting for a principle with no boundaries of scope or power?
Section 129 does quite a good job in setting up the key 'parameters' for the Voice in section 129(ii). The section does deal with principle, but the principle also has some boundaries. Drafting and debating the proposed change to the Constitution has been time-consuming enough over the past year or so without drafting and debating the implementing legislation at the same time.
In any event, legislation can readily be changed, so agreement on its current form would not necessarily be lasting. Once the Parliament moves to consider the implementing legislation, it is almost inevitable that one or more parliamentary committees will be established to consider it. Members of the public can have a further say then, either through their own members or directly, in submissions to a committee.