I would need the option to delete chunks that are defined by coordinates instead of in-game located pointers with the wand. The reason is that is is impossible to delete outer regions of the map with the wand. If I walk to coordinate 1000,1000, and set this as the outmost coordinate of the chunks to be deleted, the game already created a map stretching beyond that point.

So ideally, I would need a script in-game that would allow me at least to select all chunks that are south/north/east/west of the current location for deletion

I have a ~6 line Python script that does this. That's probably a better idea.

Sure, whatever you have is fine :)

Err, a bit more than 6 lines:
https://gist.github.com/814146