One of the major tasks in this post is to figure out how to link <cit>, <q>, <quote> and <bibl> tags to the xml:id attributes of <biblStruct> elements containing details of the cited work. The key attribute is not available on these tags, so we're left with three options:
ana: indicates one or more elements containing interpretations of the element on which the ana attribute appears.corresppoints to elements that correspond to the current element in some way.ngives a number (or other label) for an element, which is not necessarily unique within the document.
The first smacks of tag-abuse, because it's really meant to point to an analytical interpretation. The third is a multi-purpose attribute which is available almost everywhere. corresp seems most appropriate, especially for <bibl> tags (it's less suitable for the other tags, but it would do at a pinch).
Adding this as a task, because I need to search the TEI-L archives for any discussion of this before, then lay out my proposed solution (corresp and get comments.