My thoughts exactly. I wonder if they'll make it easy to re-create with a newer image. The compiled app binaries are usually copied into the image via Containerfile with no way to update it from inside the container.

Edit: it's addressed in the Proxmox board:

https://forum.proxmox.com/threads/proxmox-virtual-environment-9-1-available.176255/

That one of the major reasons for why it's a tech preview, i.e., it's a bit involved. You basically need to create separate mounpoints for the data volumes (they are logged in CT create task) and then one can create a CT from the new image and move over the data volume. Making this simpler and more approachable is on the roadmap, but no promises how fast we can deliver here.