There are switches that tell the ECU that 4L is selected. The ECU will then allow ATRAC.
You could hack into that circuit and add a dash switch similar to the no-nannies hack.
The no nannies hack tells the ECU that the rear diff is locked, so disables ABS, TRC, & VSC. That is probably something that will help you, as well as the rear diff lock anytime hack.
I can see why you want ATRAC in 4H for snow - interesting to see if you succeed.