Jhong, can't thank you enough for the work you're putting in on this, it's going to be a really great mod, awesomely useful.
But I don't really understand what you're saying above - the way you've written it in the roadmap it sounds like each phpbb user will have their own blog - and this is accomplished with a standard wordpress install (without wordpress mu) ??
Yes - by just adjusting the templates.
Think of it like this: The main blog page is using your default template that you set in WP options. There's an introduction, a link for users to set up their own blogs.
Then below that you have "Users blogs", - a list of links to your users blogs (+ maybe "featured blogs", "popular blogs",... that kind of thing, whatever floatsa your boat).
The links just go to the author archive for each author who has posts. Then the integration package detects if this is an author archive, or a single post by one author, and switches to their chosen template (and imagery). It's _that_ simple. Bits of pre-alpha code work - so it's proven possible... will just take me a while to package and release.
I didn't want to allow users to customise CSS, or template files, due to the security issues. In the future I could add some way for users to have their own categories, but this will be after the 1.0 release.