F-16 Block 100 - Proposal
As well as other countries looking at upgraded models (called Blocks) of the F-16, the US needs a highly-upgraded F-16 as a 1/2-priced and more nimble alternative to the F-35. Improvements would be in fuel load and survivability for patrol/strike missions of the Air Force (alongside the F-15) and compliment the F-35 on Aircraft Carriers (like the F-18 was to the F-14). Technologically the F-16 is very modern and only small tweaks, along with physical design changes, would make it a Gen4++ aircraft, greater than the current F-18 or EuroCanards. Like the current F-16, some systems wouldn't be available for export.
Here's the physical changes. Keep in mind airframes are full-packages where one change affects everything else.
F-35 development and production has made lightweight, stealth and bullet resistant wingskins and backstraps available and relatively inexpensive. Greater production only drops price further.
To improve range, some F-16s are already outfitted with CFTs (Conformal Fuel Tanks) atop the wings, alongside the back. This increased fuel load and location should be a permanent feature incorporated into the new, composite F-16 wing and back, but reshaped as a smoother curved surface integrated aerodynamically.
Additionally, the F-15 has proposed a variant of their CFTs instead designed as internal weapon bays. This 'cleans' the surface for a lower radar cross section as well as improved aerodynamics. There's enough room above the landing gear doors, below the wings on an F-16 for a single-door internal bay housing either one AIM-120 or 2 HellfireIIs or 2 AIM-9s on each side (the F-15 shown is dual-door). The increased sectional area below the wing from these bays would be offset by the greater increase above the wing from fuel.
But all this increased sectional area kills the effectiveness of the horizontal stabilizers (tail). Moreover, what's the point of reducing cross section if you keep the vertical tail - reflecting like a billboard - as well as the old inlet? A "stealth inlet" was developed back in the late '90s. A more substantial change to the F-16, required by the add-ons and stealth reduction, is to make it a V-tail like the YF-23 BlackWidow. This would require greater development of the fly-by-wire software, already needed from changing the aerodynamics, but also F-16 pilots would need to retrain for the V-tail.
The "America Special" would get one last upgrade, not to be exported. Conversion from the F110 engine run for decades and all across the world, to a single F119 powering the F-22 Raptor. The F-16 really needs the increased power to compensate for the add-ons as well as the low heat signature to complete the stealth development. The 2D thrust vectoring, higher supercruise speeds for greater range are both bonuses, as is reducing maintenance cost for the F-22 by reducing F119 cost through increased production.