I won't say the safety argument is meritless. But it is not the whole story.
Companies also use software to exert control over users and extract more money. By moving functionality from hardware into software, they can use both secrecy and laws like DMCA to restrict users' knowledge, ability, and rights to repair and modify their stuff.
The safety argument only makes any sense because so much of the system has moved from hardware into software, and this often makes the product worse, not better (e.g. your Jeep example). Compared to hardware, software is brittle, unreliable, complicated, and exploitable. However, it allows for the feature creep that marketers love and, perhaps as a byproduct or perhaps not, it transfers legal and operational control from the "owner" to the manufacturer.
If you are as committed to user freedom and well-being as you are to safety, then I urge you to modularize your vehicle design so that the safety-critical software you describe, such as auto-guidance, is completely separate from software used to, e.g., diagnose and repair mechanical problems. Then you can keep restrictions around the first kind but not the second. It sounds like, based on frustration with John Deere, you may be rewarded by the marketplace.
I actually agree with this statement and to your credit, a lot of the design work I do follows some of this.
Keep in mind that these are factories on wheels which means not only do we consume a tremendous amount of data, we also generate it. For example, 3D maps are built on the fly to show the customer where product has been sprayed, seeds planted, etc... On these vehicles, it's quite typical to see 1GB Data/hour generated which for an embedded device with no traditional hard drive, that's a lot. Flash memory is susceptible to extreme heat/cold so we have to be creative in this regard too (I can't talk much about this but suffice to say it's challenging).
That being a case of many, there is always a trade-off between performance and what you can reasonable keep separated either within the same PCB or between separate modules.
Thus, as much as I would like to keep separated, you simply can't sometimes. Current state of the art only allows for so much.
Companies also use software to exert control over users and extract more money. By moving functionality from hardware into software, they can use both secrecy and laws like DMCA to restrict users' knowledge, ability, and rights to repair and modify their stuff.
The safety argument only makes any sense because so much of the system has moved from hardware into software, and this often makes the product worse, not better (e.g. your Jeep example). Compared to hardware, software is brittle, unreliable, complicated, and exploitable. However, it allows for the feature creep that marketers love and, perhaps as a byproduct or perhaps not, it transfers legal and operational control from the "owner" to the manufacturer.
If you are as committed to user freedom and well-being as you are to safety, then I urge you to modularize your vehicle design so that the safety-critical software you describe, such as auto-guidance, is completely separate from software used to, e.g., diagnose and repair mechanical problems. Then you can keep restrictions around the first kind but not the second. It sounds like, based on frustration with John Deere, you may be rewarded by the marketplace.