I hope when crystal moves to v1.0 that they rethink or expand upon how shards are handled shards because right now they're hosted mostly on GitHub, and if the repo changes all projects that rely on that shard will be broken.
Maybe not a CDN but maybe some form of caching could solve this. My amber project had to redownload all the assets after failing six times, I could image this being more frustrating if I was deploying live or something.