I haven't read the recommendations of the TWG so probably shouldn't be debating it until I do but, most other countries made concessions when they brought in goods and services tax to alleviate the regressive nature of the tax. NZ didn't which in my view makes it more unfair but this is outweighed by its simplicity which is great. I was disappointed to hear about proposals for exemptions for fresh veges, don't dick around complicating things, it may not be fair (what is?) but at least it is easy to understand. Just make sure it doesn't rise above 15%.
Make a capital gains tax as simple as possible too that way people will no where they stand and there is less wiggle room for the people wanting to avoid paying it.