While the slots are connected via the network, the machine are made by the same companies that make machines for Vegas and other land based casinos. Technically you could create a machine capable of this, however, to have machines with special software that would allow the cruise casinos that much control over the payouts would be impractical. So no, I don't believe they would bother with making the machines "money spent on the cruise" aware.
Dwayne's story of being picked for the prize wheel because he is a Player's club member is MUCH more likely to be a case of rigging as the host can easily determine which players get put into the pool of names to be picked.
Slot players are (well ok... all gamblers I guess) superstitious by nature and the randomness can lead to all kinds of patterns that make it look like something could be fishy, but there is also a lot of losing going on by those people in the more expensive cabins that no one notices.....
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007