How about this? GST is a consumption tax. What about a tax on bank transactions? If you get money into your bank, i.e. salary, its not tax as is the case now. If you transfer finds to savings, its not taxed as is the case now. If you save, no tax, same as now. If you spend its taxed. The end goal is same revenue but much less admin.
Would probably make people not want to deal with banks, and possibly buy and sell in things like bitcoin. Also wouldn't that mean that all house sales would be taxed? So that would make house prices even higher.
I don't think the current system is that broken, but we do still seem to have a lot of cash jobs occurring. I fully believe in everyone, including foreign owned companies, paying their fair share of tax, as it means less reliance on charities.