A big problem with sending so many tourists to the ISS
is that they'd probably overload the life support systems. I've read that even when the Shuttle visits the ISS with a normal crew of 6 or 7, it puts a strain of the ISS's ability to scrub CO2.
A hotel module would need to be as self-sufficient as possible to be a practical addition to the ISS. It'd need extra CO2 scrubbing capability, an independent electrical supply, consumables like water and O2, etc. If you're going to go to all of that trouble, why not develop a Transhab-derivative free flyer and be done with it. You wouldn't have to worry about coordinating your tourist flights with the ISS operations schedule nor would your tourists interfere with the ISS in any way.