Comment 3 for bug 1039513

The end goal is for downloading to use simplestreams data, and for us to have simplestreams data describing each of
 1. installer kernel/initramfs
 2. maas ephemeral images
 3. fast path images (if different than 2)

So we hope to use that data, and then also use the sstream-sync client (or an improvement upon it) to pull this data down. That client will then correctly check signatures and sizes and support mirrors.