I think that something like this battery tender harness might be adaptable as a solution as a quick connect device that you could install permanently on the batts then run the wire out a small hole for easy connection without having to unscrew the steps.
http://batterytender.com/ring-terminal-harness.html
(Lots of folks use these on motor scooters/cycles to have an easy way to recharge without having to unbolt stuff.) Obviously, you could dummy something like this up with some wire and a crimp tool but this is so cheap, it is hardly worth the trouble.