The emission controls are to control emissions, nothing else. I've had no trouble with mine save for a sensor at 45 hours. Other than that it has been utterly faultless. You will still get fuel and ECU issues no matter whether you have emission controls or not.

As for who wants a 200hp 4 cylinder tractor, well me for a start. 150hp is nothing much for 4 cylinders now and will run with the best 6 pots. There is a replacement for displacement, it's called good engine design. We have just taken delivery of a 8.4 litre tractor that peaks at 400hp, not sure why lopping 2 cylinders off the same motor couldn't comfortably develop half the power.