I cannot help with clothing optional spas, but Staying at the Bellagio, Aria, The Cosmopolitan or other hotels on Las Vegas Blvd will put you in walking distance to most shows on the strip.
For outcall hiring or just hosting hookups, some hotels may require card access to get to the elevator. I remember The Venetian/ Palazzo had a person checking cards before getting to the elevators and Bellagio also required key cards for elevator access, so you may have to meet your guests in the lobby if you plan on hiring, but it's not issue getting them to your room/suite.
For shows: I'd recommend using Visit Las Vegas for finding shows of interest during your trip, you can also cross-reference that with reviews on sites like Tripadvisor, though others who frequent Vegas on here may be able to share their recommendations and experiences.