Use the showkey command to find out what keycode the caps lock key generates (mine is 58), then add a line in your layout file to the effect of
keycode 58 = Escape Escape Escape Escape Escape
Finally, load your new layout using loadkeys /usr/share/kbd/keymaps/i386/{yourlayoutname}/{yourlayoutname}.map.gz
sudo loadkeys keys.kmap
This works, but I haven't set this up to load on startup yet.
Use the showkey command to find out what keycode the caps lock key generates (mine is 58), then add a line in your layout file to the effect of
keycode 58 = Escape Escape Escape Escape Escape
Finally, load your new layout using loadkeys /usr/share/kbd/keymaps/i386/{yourlayoutname}/{yourlayoutname}.map.gz