Thanks for answering.
@bunk58, yes, I guess you just misunderstood my first post, thats exactly what I try to achieve.
The problem occurs when I try to do <base href="[(site_url)]"></base> (this might be stupid, but it’s suggested here:
http://wiki.modxcms.com/index.php/Making_QuickEdit_work_with_Friendly_URLs, and as far as I can remember, a couple of other places as well.) and base changes and breaks all paths to css files whenever I go to an article one level down in the hierarchy, or when all links in menus from my-domain.com/parent/child.html points to my-domain.com/parent/parent2.html, when they should have pointed to my-domain.parent2.html, because wayfinder seems to use site_url internally.
(OK, i guess the above was not clear, this is what I meant:)
root
- parent1
-- child
- parent2
BTW: The problem is solved by just commenting out the code to find base_url and site_url, and just hard coding them. Might break something else, but so far it works nicely.