Not much other than a reasonable hight mud flap on the rear of the motorhome. Onf my 13 round trips by RV to/from Alaska, I have only pulled a tow one time. Most of our trips have been in a Class C and the last 4 have been with a truck camper. The 25+ years I lived in Alaska, I did a lot of towing in state, either a boat or a vehicle behind our RVs. I liked the brush type of mud flaps better than the solid ones, but either need to be up far enough not to drag the ground when you hit a dip or hole in the road.
Some folks like the gravel guards that stretch between the toad and the moho like a blanket, parallel to the ground. Don't know if they are necessary or not, but if a person feels more comfortable with one, go for it. I now have a Jeep Wrangler that I tow here in the lower 48 and with the straight up and down windshield, I have some concerns with it catching a rock or other debris, but I haven't done anything about it.
Some folks just tape some bubble wrap over the glass in front including the headlights and leave it on till they get farther south. Since you have driven the Alaska Hwy in the past you no doubt know the secret to keeping vehicle damage to the absolute minimum is keeping the speed down, coming to a crawl if need be in the construction zones.
Here in Florida, where I now tag my RVs, they require full coverage on glass, so I don't get too concerned and figure if I break some glass, I will have it replaced when I get home. I cracked one windshield in Iowa on the Interstate, in 2004, had it fixed at a glass place in Roundup Montana, then got it cracked again on the Kenai when a guy still running studded tires pased me and threw a stud back. Then on a later trip. 2006, cracked another going into Valdez when I met a dump truck hauling a load of gravel without a cover on it. Other than that, not much in the way of problems. Back before the Alaska Hwy was paved I did break the upper front window in our truck camper, with a rock my pickup front tire slung into the air and I managed to hit it. LOL :P