I'd either go with WP -- well-established, open source, and requiring little or no hacking -- or plunge in and write a Paste-deployable blogging app yourself. I have a feeling that there's some demand for solid, extensible Python blogware right now. You might not care about that itself, but it would also inevitably drive interest in (and understanding of) Paste itself.
I'm in the camp that thinks writing one's own is a useful exercise. I plan on converting my own PHP5/SQLite system to Django "soon."
You could always try Typo!
Oh, and for markup, what about Markdown? I've written a couple hundred posts in it now and I just keep liking it more. Clean syntax, just enough power (for me), and few warts.
It was a useful exersize; I learned a lot from this software. Now I'm finished learning and just want to blog ;) I'm guessing that WP will require less administration than Typo, but I wouldn't be opposed to Typo on principle or anything. I notice there was a threaded comments patch that was not applied: http://www.typosphere.org/trac/ticket/135 -- that disappoints me. Maybe because I talk about fairly technical things, I've never felt bothered when there's been discussion in the comments. Discouraging discussion by making it hard to follow hardly seems like a constructive practice.# Ian Bicking