Hmm..... open in the rain while driving would be a challenge. I gather that properly designed Wiley windows are OK for camping in the rain.
Just kicking the idea around, but picturing a 5 x 10 (external dimensions, given 2" foam, will be 5'4" x 10'4" and 4' height inside, so 4'4" external height), I'm thinking doors on both sides up front, Gamma Seal "porthole" windows in the doors, and Wiley windows on those. Then, on the side walls toward the rear, "porthole" vents, just screen & Gamma Seal, because it's only opened for ventilation.
I'm going to bevel the top front down 6" or so, maybe drop the rear top a foot in the last couple of feet. We were toying with the idea of just setting a plexiglas window into that beveled portion, not to open but for light. Just seal it in with lots of silicone. Mostly came to mind because I already have scraps of plexiglas around the place.
On a completely different thought: I see people put diamondplate on the front of trailers, to protect against small rocks, sand, road debris that gets kicked up. An extra layer of 2" XPS foam would be cheap and weigh almost nothing, and it would probably take a few years of trailering to wear it out. Just think of it as a consumable, sort of like ablative shielding.
John61CT you are making me think outside of my box. There's no rule that says vents have to be on the sides or the roof. Gamma seals have pretty good gaskets, so a person could do front, rear, or floor vents.