Export to DocBook must be proceed through three steps:

1. First user chooses option "export DocBook" from wiki page (or just Export, or Save Page..) Script analyses possible DocBook converters for this system, available extensions, templates for DocBook and...
2. User chooses which intermediate (i.e. DocBook) or final (i.e. HTML, PDF, ... plugins?) format he/she wants, possible templates for this format (in directory templates\docbook). Templates are not those of Smarty, but XSLT or others if necessary extensions are available. Additionally User chooses if he/she want to dump one page or structure of pages in one DocBook/PDF/HTML/... .
3. Third step is necessary if user wants to dump a bunch of pages. On this page he will see whole structure, to which this page is linked together with all backlinks and forwardlinks.

It might look like tree structure:

o Structure (Save ThisPage with...) -up one level- -show whole structure-
o - wikipageone
o - wikipagetwo
o - - out_of_structure_wiki_page
o - - back: userone
o - - back: documentation
o - wikipagethree
- - ext: http://somesite
o - - out_of_structure_wiki_page
o - wikipagefour
o - - back: another_wiki_page
o - thiswikipage
o - - wikipagetwo

where o denotes checkboxes which pages to include

There must be a siple mapping from most DocBook tags to Wiki tags. It is yet to decode if this mapping must be one-to-one or many-to-one. In the first case all transformations are lossless, in second they are not.

Search for best match for DocBook tags to Wiki tags.
Wiki code research to find the best solution how to realize this feature.

Ruminations on DocBook V.next
More Ruminations on DocBook

UserPagetechtonik

P.S. I'm (UserPagetechtonik) not an expert in DocBook and I can be wrong in some concepts, so feel free to correct any errors if you find any.