"It is known that there are an infinite number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely the products of a deranged imagination."
There is a number of ways we could do a sexy space adventure in the hitchhikers universe. Someone could play the character equivalent of Zaphod Beeblebrox who stole the Heart of Gold after becoming the president of the galaxy. Then he/she could wander the universe getting into trouble with various hitchhikers and maybe some survivors of the planet earth after the vogons blew it up.
Nothing wrong with taking the characters from the books as arch-types and making entirely new characters for your personal tastes and kinks. Someone would have to play a Arthur Dent equivalent, in the sense that he is the only one that has any sense. The sort of person that likes to point out that there is a hull breach, which may warrant stopping the orgy long enough to deal with this minor problem.
I will control the setting and the plot twists and story, along with being Eddie and Marvin. Gotta have those two.