Hi,
I came here to ask for the same thing - window resizing from whichever corner the cursor is closest to. I'm gutted (and massively surprised given all the other achievements in BTT!) to hear it can't be done.
For anyone else who finds themselves here, the link in Andreas' last post got merged with the word "for" after it, and leads to a "page not found" error. The link should be "Resize window below cursor" only resizes from bottom-right.