Making a dumb tractor for the use-case of dumb tractor is obviously a winning idea.
I just don't think you're going to effectively compete with big agtech by putting a bunch of parts in a box, shaking it, and hoping you end up with a beautifully integrated solution. Integration hell is the reason big commercial firms dominate when it comes to large integrated systems.
admittedly, i'm not a farmer nor an expert in data driving farming. but getting a farmer the ability to precisely drive a tractor in a field so that planting seeds, applying fertilizer, and any of the other steps would be a huge win. The settings used when doing that can easily come from bigFarmData gained from other sources. Can it be used even more precisely when everything is gathered/integrated by one company? That's a question that I'm not by default saying yes to, but it seems like you do think that is true. Even if it is true, does that mean the difference from a farmer going broke because his DIY tractor behaved slightly differently than your solution? I'd posit that a farmer only being allowed to play the bigFarmData game by only being allowed to buy from one vendor that is expensive while also forcing any repairs to be expensive will cause farmers to financially unnecessarily struggle.
Why not? They sell telematics systems separately from cars. It’s possible to do this and it might not be too difficult depending on how the system is composed.