Multiple database backends can be joined virtually into one DB for
ewiki using this extension. Needs a bit more setup, because you must
assign one of the backends as main database, where changes are
written to (exclusively).
prev << "db/rpc"
next >> "db/ext_subwiki"

You cannot modify the README.plugins file, but anyhow any ideas or suggestion should as usually get filed on BugReports, UserSuggestions or even better the README.plugins.Discussion.