I have just spent the most extreme weekend for quite some time, marshalling on an adventure race. This involved carrying 100m climbing ropes & kit plus camping kit (rucksacks weighing around 40kg) for 8km over rough ground, ending with a scramble up very steep ground to top of rock buttress on high Lake District Fell, then descend to camp 1st night, then climb again to set up abseil, then walk down to camp near base of buttress, waiting for teams to arrive, which they did at irregular periods from about 2000 (last light) through 2nd night, very stormy dark period until 0330, when we all finally got a couple of hours of sleep before getting up to eat quickly, pack up kit, carry out same 40kg rucksacks, slightly downhill this time, but streams much fuller of water. Only enough space for my tiny little tent (fortunately a flexible hooped design, as rigid poles would have broken) among the rocks, and had to use rocks instead of pegs, as not much soil within reach. After walking out, had to drive about 1 hr to race HQ, where hot shower and a long sleep never felt so good! Had to replace one guyline back home - severed by rubbing on a rock.
I coped fine on MDI, but I'm really not sure a pump could have coped.