So, we have: 1) Blackbox on-board computers, probably dozens of subtle configuration variations 2) Blackbox binary-only, possibly obfuscated firmware 3) Possibly TiVo-ized runtime. 4) Farmers as the ones who'd possibly be interested. 5) Then, manufacturers could sue for various DMCA violations

I'd say the odds of this happening would be some 1e-3 a year.

This is a policy issue that shouldn't be attacked technically. Better get the farmer write their Congress members.