Something before sleeping: I found that there is another KDE-building tool, called kdesvn-build.
It has a nice documentation together with a nice guide. Now I am using it on a special prepared user (which is much better than testing with the standard user like I did last time). I will give it a try, amybe there will be time for some new screenshots 😉
The only thing I really miss (in general, not in kdesvn-build) is a anonymous kde svn mirror. It takes a long time to get all the sourace code
And for the future: it even supports KDE 4 now, and I will give it a try when I have time and KDE 4 has the first real improvements (at the moment they are “only” porting the old codebase to QT4). If it really works as expected, than I will post news more often 🙂