Technofreak: The government isn't double taxing PHEV's. In fact a smart PHEV owner using a PHEV as intended will pay the least of any vehicle owner.
RNZ talks to a rural owner with 15km of range left on his Outlander who was happy to drive the car until it's end of life, now looking at selling or removing the plug and recertifying. Waka Kotahi can't provide advice on that until April 1st.
https://www.rnz.co.nz/news/national/508403/hybrid-owners-trying-to-remove-plugs-to-avoid-road-user-charges