i already employ that idea when running the a.c.
got a small fan at wal mart with a clip on it, 12 volt
with a 9 foot cord. less than 10 bucks.
i plug it into the rear tv outlet and clip it to the top of the room divider. it moves enough air to evenly cool the trailer.
i'm sure i can do the same when heating.
my main concern would be the tanks as brett pointed out. i have never had freeze problems down to 10 degrees.
right now my trailer is fully winterized so the tanks are not a problem.
i did notice if i run the heat strip and fan on the ac in tandem with the furnace the whole trailer is more evenly heated.
really it is just a minor problem, i think the louvered vent outlet is the way to go. very inexpensive fix. in addition to checking the vent hose route.