Over the years I have sure seen a lot of "protection idea" mounted on the front of vehicles headed to Alaska, but only on the north bound lane. Many/most of these contraptions got removed and thrown away somewhere on the trip. Many caused more damage than what they prevented. Chicken wire and two by four enclosures were always popular with some. LOL I regret that I never took any photos of some of these.
I put 1/4 inch hardward cloth in behind the grill on my trucks or motorhomes to keep all the bugs and junk out of the radiator. My current truck is wearing a "store bought" screen on the outside like Veebyes mentions. It is not just the small bugs, but at times I have run into swarms of bees and butteflies. Then if you hit somewhere that the cotton wood trees are putting cotton into the air, often in Montana at the right season of summer, then that needs to be kept out of the radiator fins as well.
I also broke the upper front window on a truck camper, with a rock that came off my truck's front tire, We were able to watch the rock get tossed out ahead of us and as in slow motion, we watched it come back and hit the glass above us. Visqueen and duct tape till we could get to a glass shop. This was back before the Alaska Highway was paved. On the lower part of the 5th wheel, under the overhang, I have seen rigs with diamond plate aluminum permanently attached that looks good and offers good protection. Our current 5th wheel has some sort of a poly plastic on that area that looks near to being indestructible. Now we have never hauled this trailer to Alaska but have taken it to western Colorado, Utah and back home with no damage.
Maintaining a speed appropriate to the road conditions, seems to be the only thing a person needs to do to prevent most damage. Remember the road is not moving, only your RV is doing so. How hard the rocks hit is directly related to how fast the RV is going. I have cracked two windshields in the last ten years of driving to Alaska, one in Iowa on an Interstate and one going into Valdez when I met a loaded dump truck running an uncovered load. Both I had fixed at glass repair places and my insurance paid the $35. Many folks just up their insurance glass coverage for the trip and/or get rid of the deductible. Here in Florida, full glass coverage is required for everyone. Before you do too much to protect your headlights, check to see if the covers are glass or plastic. I have never covered my headlights and don't remember ever breaking one, but something that minor I might not have filed it to memory.