I like your idea a lot - I'm going to use QuickKeys to do this right now! QuicKeys is smart enough to know if you are in the Finder so it could still function in Word to go to the beginning of a line.
As a standard feature, it might be nice for new Mac and OS X users who are tired of Windows (you know, the ones Apple seems to be targeting in all those commercials - though could they choose someone a little less dorky now and again - I'm sure the focus groups all said, "Yes, we like him - he's a real dork I can relate to...") - any way, I digress.