Maybe even have the whole coordinate of the block under the cursor. I just realized this information is available through the '?' cursor, so I guess my suggestion is just a matter of convenience. Another way to do it would be to put the coordinates under signs - stations, towns, etc.
I checked out the trunk from svn and am having a quick browse through the source, but I do this kinda stuff all day at work and I'd rather come home and play the game - so don't hold your breath

The most difficult part is getting into the code.. if someone can point me in the right direction maybe I'll have a go at it. Is the in-game cursor OS-independent?