Quite frankly, I like the idea of a bikini carwash but not topless.
Actually, bikini carwash is a term that is sometimes used to describe a local charity carwash – kids in shorts, tennis shoes and t-shirts hand-washing cars and supervised by parents.
I’ve supervised quite a few charity carwashes as my kid was growing up and that is how we marketed the venture; bikini wash.
As a business model, there may be a niche to prospect in Vegas.
However, I believe you would stand a better chance if you fashioned the wash as a legitimate business.
For example, dress workers in “G-rated” Hooter style uniforms; meaning no cleavage or buttocks exposed and tennis shoes instead of high heels.
Not as sexy as an actual bikini or “less” but it would certainly be more palatable from the general public’s perspective.
Also, instead of trying to hand-wash with water and having to contain and dispose of waste water, you may want to consider hand-washing with one of the water-less carwash products.
This may be an attractive alternative to your proposal considering the conservation measures that are in place in the region.
Opportunity is often determined by examining what is possible from what is available.
In other words, start with the overall market and removing the pieces that are tapped to identify the relevant portions of it.
Maybe you will find an opportunity were others only see disruption.
Hope this helps.