Right, so they're going to reengineer every last subcomponent of every last part to withstand cryogenic temperatures, specifically for production in the tiny volumes needed in the space industry? Just for the inconvenience of reusing an upper stage?
Again: contrary to would-be-rocketeer imaginations, launch costs are not the be-all end-all of expenses when it comes to space. Engineering and low-volume production is killer. Mission designers always heavily stress TRL (Technology Readiness Level) of all components, as it's such a key determiner of mission cost. If any plan you propose involves "just reengineer everything", you do not have a plan.