The 6.7 is tuned to be able to tow the maximum weight, yet still provide economy, and acceleration. This generic tuning takes away the best of each catagory to provide the best 'all around' performance.
In keeping with inovation, creativity, what if Ford offered three different stock tunes that would enable you to have a truck that excelled at your particular driving needs, yet still maintain the warranty as Ford could set the perimeters.
Horsepower wars, torque wars, ads would be redefined... "set your truck to tow and have 800 lbs of torque available from 1200-1800 rpm, set your truck to economy and cruise highway speeds at 24 mpg."
Just an idea.... whose time...???
It's an interesting thought, but within the emissions limits they have to meet, Ford already offers you all those tunes. Want the economy tune? Put a brick under the pedal. Torque tune? Floor it.
When you talk about the aftermarket tuners offering you greater fuel economy, they usually do it by blowing the NOx limits out of the water. Less EGR or no EGR, advanced injection timing, reduced backpressure from the VGT, those sort of things. All of which go well outside the emissions limits that Ford has to meet.
In the old days, when lots of things were mechanically controlled, it was a lot harder to offer the best economy and driveability at all points. You often had to compromise between what some mechanical thing would do at peak power and how it would act at light loads. With everything now electronically controlled through some rather advacned software, you really can optimize everything. That's why I've always been so amused at either the claim (or the reality) that the high horsepower tunes get the best fuel economy. That's either not true or it shows the tuners don't know what they're doing, as there's no reason the lowest horsepower tunes couldn't run exactly the same way at light loads.
And even if Ford offered all those tunes, they'd have to certify them all on emissions, test 'em all on durability, etc etc. Lots of extra cost for really no gain.