Lunchbox lockers are a breeze to install and don't necessarily need to be done at the same time as a regear.
Why do you want a locker for 1% offroad use?
I run a spool in the front, and if it weren't for having a cable disconnect on one side for 3wd, I wouldn't be able to turn on snow-packed roads. An automatic locker will behave the same way as it is locked under throttle. You'll have to let off the gas to turn, and it'll lock again as soon as gas is applied, which could be scary part-way through a turn on a snowpacked road.