Two thoughts on this:
- binaries will also be able to be pinned to specific versions, since one version of the manifest specifies concrete versions of the binary artifacts through checksums. The pinning is even slightly stronger, I don't think we catch deleting and recreating a tag.
- my take on the opt-in for specific packages is that this is more of a workflow feature for individual tools to figure out than part of the core manifest (mentioned here). If we agree that this is true, it might make sense to mention that in the proposal.