There is no point in paying a tax if you don't have to. If the question is where you can and cannot go in the med in a NZ registered boat the answer is you can go anywhere more or less. You would have to pay VAT after 18 months in the EEC, with it being uncertain as to how long you have to leave before starting a new period.
You can leave the boat in Turkey
for the winter.
"ARTICLE 46. LEAVING YACHTS IN TURKISH MARINAS
Foreigners may leave their yachts in Turkey at a licensed yacht harbour or yacht docking
area for the purpose of storage
or repair, for a period of 2 years, and may leave the country using any form of transportation they choose.
In such cases, arrangements should be made to take the documentation
supplied by the yacht harbour (i.e. contract
copy and letter of authorisation), to the relevant regional customs
Yacht owners may leave their yachts for longer periods, up to 5 years, provided that the yacht sails
from the harbour at least once every 2 years. (R is not necessary to leave Turkish waters).
At the end of 5 years, the Ministry of Tourism has the right to extend the permitted duration of stay."
Some do this to avoid VAT.
A change about which I was unclear is that all nationalities now face new visa rules in Turkey namely one is granted for 90 days in any 180 day period.
That should allow ample scope
to move fairly freely.
On my recollection your longer term plans and circumstances were not explicit.
Enjoy your cruise
and yes I might take a drink as we have not had a summer here this year.