I wonder, wheter it would make sense to allow for a simple definition of Wiki markup? Most Wikis offer the same, or very similare, functionality. The additional functionality could be translated into markup by regexps.
So, this plugin would offer a preferences dialog, that contains all types of Wiki stuff like:
Links (external, internal, special like bugnumber, etc. (as regex))
So, the user configures the beginning and the ending of such a markup tag and, maybe, assigns some stylesheet to it, or whatever. And then it would simply be exported to HTML with a matching stylesheet for that Wiki.