Radisson (pre Regent days) did a 26 day round trip from west coast to Tahiti with return thru Hawaii - As far as I know they've only done it three times but the ships were full!
I'm sure if they shorted it to a exclusive Hawaii itinerary they would find a lot of interest and many new passengers who would get "hooked" on the Regent experience.
On one of our trips back to Hawaii we stopped at Fanning Island - on the other voyage, Christmas Island - they were both very interesting and definitely "off the beaten path"!
Margo