Replying to myself for update: You can now try out an external import-only site at:
http://magnusmanske.de/wikipeerdia
("wikipeerdia" was jokingly suggested by Brion a long time ago :-)
How-to: * For testing, anyone can import * Importing is done by clicking on a red link, or on "edit" on an existing page * The import page will show the current en.wikipedia version * You can chose another version in the column on the right * Click the "import" link for the version you want to import * The import will show up as an edit, with the version ID in the comment
Currently, main namespace, categories, and templates are imported. Other namespaces, as well as all talk pages, can be edited normally.
Image import - not yet.
Give it a try and tell me what you think!
Magnus