new zealand itinerary

I would recommend joining a Facebook group called New Zealand travel tips. It's LOTS of posting of possible itineraries and you'll get the feedback you want there I think more so than here.
I've been using it for my upcoming trip to New Zealand in March.

thanks so much annemargaret

That's a really intense 27 days!
My main concern would be that some of your destinations are very weather dependent for their impact - Abel Tasman, Franz Josef, Tongariro. It's a shame you haven't got the flex to move things around to accommodate the changeable weather, which could make all the difference between meh and wow.

Don't know whether this would suit, but Kiwi experience bus could be an option? Or the itineraries may at least give some new ideas?

https://www.kiwiexperience.com/hop-on-hop-off-bus-passes

Perfect world, you'd have a car and then greater flexibility to tailor your itinerary.

well franz josef and tongariro i have a bit of flexibility.
Franz josef, I'm sleeping there two nights, and tongariro is meant to be done day 24 but i guess i can do it day 25 and go to wellington after and only have one night in wellington instead of two.
abel tasman is a day trip so that one is different...

overall what can i do? i could stay 2-3 days and the weather will be bad throughout. Even if i had a car, i'd still have to book hotels in advance so not thaaat much flexibility with adding days. Only a campervan really gives the flexibility, no?

I don't know the bus schedules, but I'd assume that there's not a lot of flex there either? Assume you've worked through that in terms of Tongariro crossing etc?

Would there be an option to strategically rent a car for a few bits where the timing is tricky? eg. Rent in Picton or Nelson and return in Queenstown? Then I'd travel Nelson to Hokitika (stop in Punakaiki, Hokitika Gorge), Hokitika to Franz/Fox or Wanaka/Queenstown (depending on the weather). I'd pick staying in either Wanaka OR Queenstown to avoid changing accomodation. More accomodation choices in Queenstown too, booking.com will give you lots of free cancellation options if you want flexibility with timing. Milford sound as a day trip is a long day, and would recommend keeping as a bus tour for this.

Personally, I don't really get the appeal of camper vans - super expensive to rent, plus cost of powered campsites, and fuel is currently $3+ a litre... But if that doesn't put you off, then maybe that's worth considering?

To give you an idea of the weather variability...where I am today it was 22 degrees (but there are wind warnings), it's flooding in Invercargill/Gore (bottom of South Island), and there's a heavy snow warning for the central South Island for the weekend! :)

In general, there's a lot more bus flexibility than I expected for a country that seemed so car-oriented. The only time real time that bus flexibility was lacking was with Punakaiki. Between inter city and greatsights, conncections could be found.

To me, it seems the lack of flexibility is not about bus vs car but about weather. If I'm reserving hotels/hostels in advance, aren't I lacking flexibility no matter what?

Yes, of course. That's why using flexible accomodation booking options such as those on booking.com might be helpful.
It sounds like you're happy with your choices and the possible limitations. Have a great trip!

I spent two months in NZ earlier this year - from mid February to mid April - and like you did it largely by Intercity bus. They were fantastic but, as you've found, it takes a little bit of extra planning around their schedules.

The one thing that stands out to be here is your jump from the North Island to the South Island: it might be worth looking for a flight to get from Wellington to Nelson, since the journey by ferry and bus is quite long and ferry delays/cancellations are incredibly common, which could leave you stranded in Wellington or Picton if you miss the bus connection. Flights are quick, reasonably priced and in good weather it's a spectacular route.

Regarding Queenstown, I wouldn't add any time unless there are specific things you want to do. It's gorgeous but I found the town overwhelmingly touristy (especially visiting right after I'd been in Wanaka).

Wellington was one of the highlights of NZ for me so I think your extra day there is a very good thing! There are amazing walks (the Skyline Track is fabulous if the wind isn't too strong) and Te Papa is one of the best museums I've visited. There are also good walking tours offered by the iSite.

Have a wonderful time!