The claim that it 'damages the integrity of the GST system' is nonsense of course. Its a tax and as such has no integrity - its simply a means (justifiably) for raising govt revenue. Two countries that adopted NZ's GST model AFTER us are Canada and Australia and they both have no GST on various essential goods including many grocery items. They adopted the GST after NZ and had the opportunity to install whatever they wanted and chose a fairer system. Also, these countries' business computers seem to handle different requirements for GST just fine and so would ours. NZ's GST system is the envy of foreign govts maybe - but not their citizens! By the way, GST in Canada is now 5% having been reduced progressively from 7% when first introduced. NZ prices for goods (particularly food items) are outrageously high compared to other similar countries. 15% GST on food & rates is legalised thievery. I dont know how people in NZ cope.
I think its more a case of they couldn't be bothered. And the Maori Party went about it the wrong way to try and get support from other parties. Instead of "healthy" they should have had "essential". And "essential" should mean essential services as well, such as power & gas. And if GST on luxury items has to go up to cover it so be it, as we now no longer produce anything in NZ it wouldn't hurt the country in any way. As for it being too unwieldy, give me $200k a year and I'll run it from my front room.
It doesn't damage the integrity of the GST system but rather reduces the tax take no more no less. And as for our system being envied by many countries name one National. Other countries have different rates for different things why can they manage is it perhaps that they have more brains and ability than kiwis? Or a Governments that actual give a damn?