Referenda for everybody

I've been thinking a lot about MMP and the last post hasn't entirely got it out of my system. Something else occurred to me.

John Key's decision to hold a referendum has been met with apprehension by most MMP advocates, although fairly muted apprehension, because it's a bit hard to stand up and say "I don't want a referendum on this issue". The only grounds one can legitimately argue with it are are cost. As I posted earlier consultation is seen as a universal good by almost every actor in our political system, and although we have no clear definition of what is and isn't consultation, a referendum seems to meet everybody's definition (hence why nobody is willing to criticise the act of holding one).

One way John Key could genuinely appease pro-MMP advocates is to say that he intends to pass a law requiring regular referendums on the electoral system every 12 years, to coincide with general elections. Obviously such a law would not prevent any future government from refusing to hold the referendums, but I think it would go some way towards calming the concerns of people on both sides of the issue - even if you do end up with a voting system you view as unsuitable, it won't be forever.