Recently as I swapped my doors and I found that my truck's doors had no water shield, I guess it got left off maybe when I upgraded speakers (and radio) ... or maybe it wasn't even there when I bought the truck used (It had a cheap old aftermarket stereo and cheap pair of speakers already in it then) . Was long ago either way. My OEM doors were pretty rusty from rust through from the inside in places, like the mirror screws were frozen with rust, but the interior window and latching mechanism are all great. I am thinking that since all my door rust was not in the lowest pinch weld, maybe the lack of a water shield was a big part of the reason for the rust. On the right or passenger door, rust had even weakened the door skin enough that I thought the mirror would pull out at the top, this rust came from within the door. My new doors are painted inside where the OEMs were not painted, but I know that doesn't get everywhere ... just where my arm and hand allow. I am going to make some water shields or "vapor barriers" from some thick plastic left over from building the house, we used it with a coating of tar to water proof my thirteen course basement walls befor back filling. It should work as really only need to cover holes in door inner surfaces.

Inside the cab is heated like your home, outside is not heated ... if it is cold out and warm inside, the cold outer skin of the door is the water shield, and the warm air can condense on the inner side of the outer metal skin, and in tame can cause rust through as this moisture collects in the bottom of the door. I know ... rain can come in still between glass and outer belt line seal. Condensation can occur all over the inner side of the skin, but rain just drops though. In your home, there is a vapor barrier where insulation is to an outside wall ... the vapor barrier is on the insulation on the inside room side to keep moisture from being absorbed and held against back side of exterior walls where it can lead to rot. Vapor barrier or door water shield does not have to be sealed tight like a boat hull, just a very close fit to window crank or door handle will stop the easy transfer of warm air to the door skin's inner surface. I did see that I added shields over my speaker back sides.

When I'm ready to seal everything as I reinstall door panels, I'll run a thin bead of that Loctite polyurethane sealer to attach my water shield over the various openings. Mean while, looking at options for door panel attachment too, hate those springy clips and my door panels already have some broken attachment points. Mean time, just gonna make some simple wooden mini arm rest to use and protect arms from sharp metal and leave door panels off so any condensation that may occur can freely dry out fast.

 

The closest thing I've found like newer vehicles is the carpet protection plastic. The stuff they put on carpet for showing new homes etc. Like a 30 inch wide roll of scotch tape. Not sure what its life expectancy is, but it sticks to carpet after couple hundred open house people trample it. Bought it at Home Improvement store.

 

it holds up pretty well, I would try it.
I have used it for other applications besides carpeting and years later it still works.
I'm not sure how well it would stick in zero degree temps since I am using it in a warehouse and basement. I'm thinking it would be just fine.