Except for self driving stuff I was arguing about. We are not yet sure who will be liable for them. Also there is pretty much self driving in some agricultural machines, for use on the fields.
But seeing this topic I'd make it possible for farmers to mod their machinery, with a complete loss of warranty.
Imagine a modded component accidentally sending false or misleading data on the CAN bus, or not yielding the bus, or simply being incompatible with a component. These scenarios can cause serious troubles.
These stuff are not JS frameworks, a page reload does not undo a bad trial and error round.
Also the supporting tools are expensive not only for farmers and machine shos, but also for vendors. I remember the price tags for calibrated instruments from my time in automotive industry...
