I think the size matters more than the strength...a drenching rainmaker would be the worst case in my opinion.
Another huge related issue will be just how far north it strikes. If it is up around Cairns (as suggested by the JTWC track projection) it will be bad enough, but if it brings a lot of rain to the Fitzroy River catchment areas further to the south behind already flooded Rockhampton (as the Euro model suggests it might) then it will be a lot worse. The further south it ends up the more densely populated the coastal strip is too, of course. It certainly looks big enough to do a heck of a lot of damage wherever it lands , but north is better than south, barring perhaps a direct hit on a city like Cairns.
I guess the speed that the high pressure system north and north west of NZ travels at will have some bearing on this?