I haven't taken my 5t off road yet but I've seen what can happen. Lots of SS videos of Haspin and Rausch Creek online of some big-time quagmire. I don't have a winch.I don't have any experience to answer your good questions, but I imagine they must be fairly tolerable, since they were supposedly standard equipment in Marine issued M939's?
I do have 2 used Detroit Locker 5t diffs that I would consider selling.
The air locking fire truck axles are cool, wrong ratio, rare, expensive, and nobody has really thrown any under a 5 ton mil truck yet that I know of. Not even sure if the width and mounting is compatible, such as the torque rod arm mounting provisions. Air brake adaptation should be straight forward for M939's? Same with adding CTIS if for an A2? TBD, none of it has been done that has been posted. I'd love to do it, especially in the front, but don't want to lay out the cash to then only find out it won't bolt up, or is too narrow, or etc.....
Have you tested your traction off road yet? You can get these truck stuck pretty good without any type of traction assisting diff.
Just once or twice, I want to attend the Rausch Creek rally. It's a bit of a haul for me down here in Annapolis.
I'll bet shipping costs of your Detroits from Michigan would be ugly.
This fall/winter, I hope to finish up the routine, deferred maintenance and then I can focus on fun stuff like lockers, paint, canvas, etc.