Since campers are more house/building type construction, I'd ask a contractor maybe? They'll know more about the feasibility of cutting a hole in a wall and the structural compromise it would cause. Honestly, I can't see where it would be an issue if properly finished off with a cross brace above the door.
Be sure to look at the entire project, such as adding steps under the door, etc.
Now-2014 Sierra 346RETS 5er BUB
Then-2002 Keystone Springdale 286RLDS TT
Nights camped in 2014-28, 2015-127, 2016-10