Well, yes exactly! It's not a new wiki. It's a library to build any wiki with you like. Or perhaps even export data to and from wiki's! By defining what happens with data using XML and regular expressions, you can make wiki's communicate, or make more than one thing work with the same wiki data. (I'll list WikiCreole with those to make a WikiParseXML for, I'm was looking into TWiki lately)

I suppose the best approach to building such a library would be to take a working wiki engine, possibly some old and mature one with large community, and improve the modularization of its components, making them usable without the need for the rest of the wiki engine in question. As for generalized parsers that can take any markup, generalized storage that can store any data structure or generalized routing systems that can take any url structure, I don't think they are wiki-specific. I mean there are lots of general-purpose utilities ad libraries that already do that.

I'm especially wary of a general markup parser -- sure, they are very fun to write, and you can learn a lot along the way. But I'm involved in the WikiCreole project and I really believe that you don't want each and every wiki to use a different markup. So writing good and extensible Creole (or any other single markup) parsers for different languages seems to me to be a much more worthwhile effort. Again, preferably self-contained ones, with minimal dependencies.