Re: Fair question
Maybe what could be substituted for a return capacity for all crew of ISS is simply a section of ISS which can function as a lifeboat. This lifeboat would connect at same location as Soyuz and create a sort of porch for the Soyuz. In a emergency crew could go here and seal themselves off from the rest of ISS (and if things get really bad disconnect from ISS).
So this lifeboat doesn't have a return to Earth capacity, but it does have the capacity to kept all the crew alive until they can be rescued by Shuttle or Soyuz. This could have say a capacity of 3 and if more people are at station, add another one of these lifeboats (and another and another:).