In a case like this, with a customer like this, I always make my customers sign a long hand written explanation that uses the words they "are routinely bypassing safety devices", with the strong assertion that I have to CMA/CYA.
In the USA, that phrase usually makes them reconsider, since that is the same wording US Fed OSHA uses to justify a multiplying factor to what ever the normal fine would have been for having bypassed a safety device.
The reason we have BDIs with low battery lift cutout, is to prevent a 'run-away' condition of the traction controls, since low battery voltage and the resulting high amperage has the potential to have an SCR fail to turn off, and at the same moment a traction contactor tip pair weld itself closed, not so much to help the battery last longer. When that happens, only disconnection of the battery at the connection to the truck, or getting the traction tire off the ground is about the only things that are going to stop the truck without a fire, (you may find a wall strong enough to slow the truck down, but if you don't disconnect the battery, that will be where the fire starts)
If you fail to "CYA", and you made a paper trail that shows you were the one who bypassed the safety control, (a work-order to bill the time) once an accident has happened, a judge and jury can find that you can be made personally responsible for the negligence of not properly informing the end user of the results of having bypassed those safety controls.
At least in teh USA, your lack of 'deep pockets' will mean that you are not alone in court, but that will also mean those others with the deep pockets will not be as interested in protecting you as they are in protecting themselves.