Several cruise lines used to do the round trip Hawaii cruise with a stop in Fanning Island; my parents did one about ten years ago. I don't think any lines do it anymore, but I really don't know why. I think my parents said it took more than one day each way and there wasn't really anything when you got there.
What I would really love to see is one way cruises between Vancouver and Hawaii. Ten days would give you five sea days and five days for the islands. It would be totally legal and Vancouver is an extremely safe and appealing destination in its own right. (And the fact that I live nearby may influence me just a wee bit!) Right now RCCL does some 10-12 day cruises like this on the way to/from Alaska, but I think this could be extended further into spring or fall, or even all summer as an alternative to the same old Alaska itineraries.
Any line doing this would make my day, but if it were Disney?