At least one of the excuses used by car manufacturers to not reveal details/etc on their engines has been that "modification could cause it to fall outside of emissions specifications." I don't see why Deere et all wouldn't try the excuse.
I own one with a 35hp engine detuned to 25hp to legally bypass emission regulation. Just a fuel regulator screw turned down and timings modified. The exact same tractor with the screw turned up is about 10% more expensive and has a DPF which decreases reliability. The uptuned model also has an ECU and is harder to repair, whereas non-emission model can be (is) almost purely mechanical.
Also makes it so you don't have to avoid breathing the cloud of smoke when it starts up or grunts, nor get black shit caked all over your loader frame. Part of me wishes I bought >25hp for the emission system. Of course it's natural to always want more tractor than you have.
As a small land owner I don't think I could find a way to put 2 hours on my tractor in a day, so that I need to recharge overnight after 2 hours of use isn't even a loss. And not having to deal with diesel would be a big savings.
Via HN a little while back, I came across a guy importing electric versions of things like front loaders, forklifts, excavators, etc. Intriguing, but less compelling if you have to buy 2-4 pieces of equipment rather than one jack-of-all-trades. Although if I were going to have to maintain multiple pieces of equipment, I'd definitely prefer them to be electric!
I can end up putting in more than 2 hours a day, but I think the math still works out for most homeowner use. I think the main thing it doesn't work out great for is long dirt-engaging operations like for actually farming a large field. But it's not like the subcompacts are really made for that either, and they're quite popular.
It would be really interesting to see what could be done with linear actuators instead of hydraulics, too. Although I suspect heat dissipation would be a problem, and working on hydraulics is pretty cool in and of itself.
Edison Motors up in Canida is going this with OTR trucks for the logging industry.
I've read before that for the average homeowner, the particulate/NOx/CO emissions from their little 5 HP 4-stroke carbureted lawnmower and 40cc 2-stroke carbureted blower/stringtrimmer/etc are often greater than that of their 150 HP automobile - which has an ECU and oxygen sensors and fuel injectors and catalytic converters and so on.
The price bump to go up to the 33 HP engine with the emissions controls was significant (much more than the 8HP performance bump), and every 30 hours or so it wants to run a "regen" cycle which always seems to be at the worst possible moment in my workload, but I feel a lot less guilty about running it knowing that my exhaust isn't nearly as bad for the environment and for my lungs as it could be at a slightly lower performance tier.