I wonder if anyone has strolled down to the old file cabinet at Lockheed Marietta and dusted off the Fat Hercules (or fatter?) file , the C-130XL. Around 2008/2009 two or three versions were being looked at, a lesser change version that moved the wheel wells out giving a constant cross section, moving the wing higher atop the fuselage, and a full blown new fatter fuselage. Wings, engines, cockpit, tail pretty much J, giving some compatibility with the regular C-130 fleets.
I do wonder about Coochycools idea for a Dornier 328 type engine swap to turbofans. Surely that would only be a last resort if the engine issues can't be fixed, and would be a majorly expensive and time consuming process for the A-400- but intriguing. Maybe that would reduce turbulence and help resolve the inability to pass fuel to helicopters and the concerns about paradrops as well?