Implement Write and Delete functions to always overwrite with the latest update. The Delete will technically be able to delete something that has already been deleted, but I actually think that is desired.
Read the hlv implicitly out the xattrs to construct a DocVersion, there is a concept of a CV without a _vv, that is just implicitly sourceID@cas (when a document is written directly to couchbase server and not replicated by XDCR).