All of this info is precovid...
Back in the day WS was fairly open to considering such things. We had a bunch of people who got off in Moorea rather than taking the last leg, but that was off early not on late. I've seen people who had transit problems catch the ship a day late, but that was with a schedule problem. You can always ask, and they can only say "no" We got off in Mubai rather than going on the Dubai, it took a special request, and there was no guarantee it would be allowed. One question might be is there immigration in Moorea, I don't know, but I think you clear in PPT.
On our itit, several couples spend the night in Bora Bora offship, and I think the ship even offered such a plan. I don't know if they still do,