Greg,
I think what's missing here is exactly what the mission is. ISR is Intel, Surveillance, and Recon. The mission is not to haul a lot of cargo or people, it's to accomplish ISR. The Merlin, King Air, and PC-12 are built to fly two pilot. The military then adds equipment and a technician to run the ISR systems. That's three folks. The F-15E has infinitely more complex systems and mission sets and it's done with 2 crew members. Making the plane easier to fly by making it a jet (Scorpion) with basically centerline thrust, and less moving parts, all make for a safer more reliable piece of equipment. Make the systems operator station marginally easier to run via HOTAS (nice to have not required) and bingo you have cut down a crew of three to two. Cargo in your explanation is actually fuel in mine (turbo props either carry full fuel, or people, not both). Fuel equates to longer time on station, which equates to fewer aircraft required to cover a vulnerability period, which equates to fewer aircraft that have to be bought, which means a smaller logistics / repair chain, which means less expensive to the taxpayer and more bang for the buck for the operator / military.
When you can almost completely remove fighters from this chain, you cut down your expenses dramatically. When a fighter squadron deploys it has a huge footprint in maintainers, pilots, aircraft, logistics, tankers to get them to / from, tankers on station to extend fighter time airborne, deployments pay, family quality of life hits, all factor in. Putting a few of these (Scorpions) in place, with their MUCH smaller footprint saves big cash, but also on quality of life for our ever shrinking but doing more with less military.
The Scorpion would not make a good replacement for the T-38 for several reasons in my opinion. First the Talon is used almost exclusively for guys going to fighters, so the plane that replaces it should be similar in performance and flight characteristics to the follow on assignments (a straight wing non FBW vice a swept wing FBW). The F-16, F-22, and F-35 are all fly by wire, and so should the next trainer. In a non FBW (fly by wire) aircraft, you as the operator have to make sure you don't overstress the aircraft, while the FBW bubba's just pull and Hal (the three flight control computers) fine tunes everything for optimum performance. The trainer replacement will need to be able to pull some G's, more than 5, will need to be able to simulate weapons deliveries that are currently being used, as well as the maneuvers associated with air combat and weapons employment. The T-50 is the closest to off the shelf in my opine that's currently out there, and oh by the way it's basically a detuned F-16.
The reason the mission set of the Scorpion as advertised is ambiguous is PR. They don't want to narrow down the potential buyers with how they market the aircraft. It would do the ISR mission much better, or in addition to the current crop. Much better.
Lastly, you might just have to trust me on this one. I can't go into detail, but having been operational in both fighters and ISR aircraft, I would go with a Scorpion type aircraft hands down.
Cheers,
Biff