making the current filters work in a fuzzy way

Requirements

should work on both the collection browser filter (both in flat and treeview) and the playlist filter
a slider could determine the grade of fuzzyness in 3 or 4 steps (eg. exact - slightly fuzzy - very fuzzy )
should work as close as possible on the current google-like filter syntax (so you can first search in an exact way, and then "widen" the search by increasing the fuzzyness)

I tried to implement a mechanism to make the existing filter work in a fuzzy way, following these requirements. For the flat view in collection browser, it now works more or less...

But now I decided to give up (not without having learned something, see below)