Hi all
To solve the external storage problem, I have written http://tools.wikimedia.de/~daniel/foo/WikiProxy.php. It's not fast, as it also pulls the pages via HTTP from the real servers, but it does caching for dewiki, enwiki and commonswiki (I can add more on demand, but I have to ask Kate to tweak grants for each new cache).
The more people use this, the better it works :)
I have also fiddeled with setting up an interface for WikiProxy that bypasses the Web Server. If anyone wants to experiment with a shaky fifo or plain TCP interface, tell me, I'll have another look at it.
HTH -- Daniel