Obviously I'm not in their place, but in hindsight, my first thought when reading their initial issue was "Why not make a container that serves the minimal subset of Rubygems stuff necessary to bootstrap Rubygems, and use that as a source in the event that the main side died and needed to be kickstarted again.

Docker itself used a similar strategy for their build process: the recommended build process uses containers to build the Docker binary, so they made a precompiled binary available that was crafted "the hard way" that could then be used for running the saner build process.