Does occasional mean some diverts from Queenstown?
I'm none too familiar with Otago's weather, but for the number of times Queenstown is closed due weather, how many of those would also close Te Anau?
Certainly if the answer is not many, and it is a viable alternate, it would be a much better proposal for the punters down the back than a divert to Invercargil and a 5 hour bus trip to Queenstown (I was almost on the receiving end of that years ago - was too young at the time to know much detail, but I think we did one missed approach and got in on the second one).
TT