Yes the proposed change to the constitution lacked detail, but that is entirely in keeping with the constitution as a whole, it is a "high-level" document after all. The detail would have come in the legislation that enacted it, with plenty of public consultation and discussion in parliament, no different to any other legislation. In its final form it would have probably looked a lot like previous advisory bodies that we used to have, with the critical difference being that it could not be disbanded just because the government of the day didn't like it.