Jet powered transports might be sensible for very large nations like Brazil or Canada, where distances between places are equal to what most nations consider "strategic", but I always thought that props gave you better fuel economy and were better when it came to making sudden changes in thrust (having to do a go-round or making sudden stops on the runway.)
Actually, since there was a lot of talk back in the late 90's about how cargo size was constrained by the generic "C-130" template (trucks and AFV's being designed to shoehorn into the available space of the C-130; apparently this led to lots of bad compromises with the US FFV program), wouldn't it make more sense to design the next generation of tactical airlifter with a bigger, roomier cargo bay (and the ability to lift heavier loads)?
The C-130 has outlasted at least two and possibly three generations of "replacements", maybe the evergreen Herc could be recast with a larger or wider fuselage attached to the proven wings/tail avionics (probably a lot more difficult than that, but I'll let the qualified people shoot at that one...)