We are attempting to provide information about the access/availability status of items in a bibliography, encoded with
<bibl>. It seems reasonable to be able to encode this information in the same way we would do so in the
<availability>, and no other approach seems available (other than the generic
<availability> is a member of model.publicationStmtPart, which shares a lot of elements with model.biblPart, for obvious reasons (
<publisher>, for instance). I think
<availability> should be a member of model.biblPart.
It presumably belongs in the content model of
<monogr> somewhere too,
<biblFull> already has it because
<publicationStmt> can appear in it.