I'm considering a configurable rendering pipeline for each supported
filename extension. So for ".mdwn" files, it would send the content through
linkify, markdown, and finalize, while for ".wiki" files it might send it
through just a wiki formatter and finalize.

This would allow not only supporting more types of markup, but changing
what style of [[WikiLink]]s are supported, maybe some people want to add
[[CamelCase]] for example, or don't like the [[SubPage/LinkingRules]].

There also needs to be a step before finalize, where stuff like lists of pages
that linked back to it could be added to the page. However, doing linkbacks
also needs to tie into the main logic, to determine what pages need to be
renered, so maybe that won't be a plugin.