That we might need to engage in constitutional amendments to deal with issues currently reserved to the Regions is a definite possibility, but if we try mixing that in with the structural reform, we may end up with people voting against the structural reform simply to block the added powers.
Conversely, if people do not believe that the Congress will be able to legislate on issues presently in the remit of the Regions, then they may well decide to keep the status quo if only to keep these issues on the table.
I have been trying to find one unitary nation where they have constructed their government in the way you propose - i.e. a government of only enumerated powers as opposed to a government of general powers that is limited by specific provision - I cannot find one.
Regardless, this discussion clearly demonstrates that whilst we all recognise the need for change, it is highly unlikely that a consensus can be easily formed presently, which could make any transition dwindle numbers further. I was IMing with somebody the other day and he told me that he was cynical about change making it through - I couldn't help but agree with him. Even when we made minor and consolidating changes to bring in the Second Constitution, it nearly all fell apart at the last minute.