Higher top tube: It's a bit higher, not a huge amount because the head tube is the same length, but may help when stopped, I've noticed what you said, and, it will reduce the moment on the seatpost a bit, always good.

Brakes: Unless the gravel trail is always bone dry, discs should really help with rim durability on those 20" wheels; I see how you use your All-Packa, it sees a lot of mud and wet dirt. That also allows the rim sidewalls to be less thickness, and hopefully, for the same rim weight, they put that weight at the spokes holes for better fatigue resistance there, that's always how I've worn out road wheels. My cheaper Dahon rims that are doubled on each side but single thickness in the center at the spoke holes, have held up surprisingly well in that area, I think it's thicker than their double-wall rims there. However the thick sidewalls are near end of life due to rim pad wear, with road-use only.