2) If it's possible to exclude a category in the site-wide blog? Then the bloggers could simply post to that category (e.g. an 'about me' category) when they want to create a post.

1) If it's somehow possible to filter a featured blog listing by who featured it? Then the user could feature whatever post he/she would like as about-me page and I'll just show latest featured from the current author.

3) Extend the user profile registration with an 'about me' section with a few custom fields. Will give much less freedom to the blogger though.

4) Manage the 'about me' in a totally different component, like Zoo, Joomla native or JReview, with the downside that the blogger is introduced to another publishing Ui, which I would like to avoid.

Correct me if i am wrong. Did you wanted to setup your site based on current logged in user? .

And from my opinion, you can hide them accordingly on your current menu item here http://take.ms/oWYPg.

This can be achieved using this My Blog menu item. Maybe you can try setup a menu item using this options http://take.ms/0U5pG. This menu will only can be accessible by registered user(logged in).

What I want to do is to extend the view of the currently viewed blogger. (blog posts from specific blogger, like when you click "more from this author" in the About the author-box in a blog post)

Those settings would really solve the entire thing, if in some way it is possible to select "currently viewed blogger" in the include box, or somehow send a filter parameter when opening the menu item, like in the "more from this author" page mentioned above?

If somehow there is a way to send a dynamic "include selected author" value to a front-page menu item - I would be good to go