I'm very interested in this and will try to spend some time and energy over the next year looking at the question of a European blogosphere. I'll let you know what's going on as I work through things.

Your point about language is one clear difficulty to a large mass blog on the dkos scale and style. However, a European blogosphere would not have to be organized on the same principles. It really might be a series of smaller regional/national blogs with interaction to a couple of metablogs. These few metablogs would likely be in English and/or French, German, and Spanish.

Can you say "subsidiarity"? :)

There are, of course, other possible models.