Exogen, thanks! I didn't knew about AsciiDammit.py before.
Although it looks like (what I've found from google) that the translat table is hardcoded to python code in AsciiDammit.py. It is not good, after all it really isn't languages problem to handle such general things. I know better solution, using iconv and it's ratherly new feature translat to convert umlauts and friends to ASCII. Unfortunately I have no time to implement that.
And yes, this was more of intended as example how you can get rid of the "My 3rd party app (for example one in contrib) uses slugify function that does not support my umlauts blah blah..."