I like the idea with the waterpark and the hotel rooms. They could function similar to apartments!
One vacation spot I would really like to see is a Venice inspired one - with canals instead of streets where Sims can do romantic gondola rides and with carneval masks they can purchase or collect. Another one would be a rural Japan inspired one, where Sims can stay in ryokans and sleep on futons, eat traditional snacks like mochi and gaze in amazement at cherry blossoms. There could also be a shrine they could visit and maybe we could see a return of martial arts? :) Everything would go with beautiful buy/build items (including koi ponds, tatami mats, a hot spring? doubt the last one because of the hot tub from perfect patio stuff) and traditional inspired clothes and hairstyles with flowers :)