I have serious doubts as to how easy it will be to modify these things. While I'm sure it would do just fine, within reason, I'll stick with a heavily modified raptor as the main fun-haver.
10mpg on road will mean 5-6ish offroad. How big is the gas tank? I'd be worried about off-road range when you're flogging it.
I really don't like the awd full-time. Furthermore, I'd be VERY interested to take a look at the front CVs to see if they'd even allow extra travel.
I think it's a cool truck for the street, but I wouldn't make room in my stable for it. Every mouthbreather with an inferiority complex will be trying to drag race you.
and fwiw, dropping a 750HP motor into a raptor costs a hell of a lot more than $20K. (i'd have already V8 swapped my truck if it was $20K, in all reality, to pay a pro, it's more than double that.)
oh and Alcantara? ooph. Make good friends with a very talented detailer. One trip into the dirt and it'll never be clean again.