Storing container images is a great use case for an object store, not a block store. They should get sucked down whole to ephemeral storage on the compute nodes.

Mounting containers to a distributed block system is an anti-pattern. This is going to go poorly.

Ceph has had some really smart people working on distributed block for a lot of years, and they still have significant issues. It's not because they're dumb, it's because performant, scalable, and available distributed block is either hard or impossible.