I ran across this;
which indicates there could be a 'simple' fix for disabling stop-start by 'hacking' the trailer tow wiring harness.I was a service advisor at subaru. the easiest way to permanently disable the start/stop system without any warning lights is to have a genuine towbar fitted, and dig out the magnet from the inside of the 7 pin plug. this way a signal is being sent to the car saying you might be towing, which disables the auto start stop system without any warning lights or other symptoms. I suspect it will probably work the same on other models. Your welcome everyone.