How about a space "tug" permanently stationed at the ISS which could be used to shuttle occupants from a crippled spacecraft up to the ISS in an emergency.
Makes sense to me.
Also a robot "droid" to inspect the outside of the shuttle in orbit.
Both could be done quickly at a minimal added expense.
Changing orbits requires a significant amount of fuel. Columbia didn't have enough to make it to the ISS, nor would have a "tug" that was based on the ISS.