HarmLessSolutions:
Claiming back the RUC component of petrol may be a solution for the small number of oversized and totally offroad vehicles currently but I don't see this as a practical approach when you consider the massive numbers of hybrids in NZ.
Owners are going to be resistant to having to both record their distance travelled (if it remains a non-automated input) plus then submitting the paperwork involved in claiming the RUCs back, then of course the processing required by NZTA. How many NZers presently claim the RUCs back for their boat, lawnmower, chainsaw, dirt bike, etc. fuel?
For clarity as the rules stand currently (when the EV temporary exemption ends), Only Plug-in hybrids would be able to claim back petrol tax (non plug in petrol hybrids are not required to pay RUC's, as all their energy comes from Petrol, which allready has road tax included in it).
But yeah, it would generate an epic amount of paperwork. Probably workable with the current number of PHEV, but could become unworkable of some of the big brands decide to sell large volumes of PHEV's.
"How many NZers presently claim the RUCs back for their boat, lawnmower, chainsaw, dirt bike, etc. fuel?"
Suspect it is near 100% of the use cases that are eligible.
Note that the eligibility criteria to claim back fuel tax is quite narrow. All that stuff on your list can only have the tax claimed back if used commercially. ("exempted vehicles" are not common).
This is quite a sore point for recreational boaties who pay a lot of road tax as part of their petrol. The government promised that refunds would be available for the Auckland fuel tax when they were consulting on it, but when the legislation came out, they reneged on that position, and only made refunds available for commercial off road use...
https://www.nzta.govt.nz/vehicles/fuel-excise-duty-refunds/
https://www.nzta.govt.nz/vehicles/regional-fuel-tax/rft-rebate-claim/
Ignore the bit about private passenger vehicles not being eligible unless they are heavy - Legislation doesn't have that stipulation. see 5 (1) (b) below, and note that the definition of licenced vehicle near the top.
Legislation here:
https://www.legislation.govt.nz/regulation/public/2004/0238/latest/whole.html#DLM277702