As far as barn doors and rain...During one big storm I did close it to about 4" at the middle, the drip rail across the top then covered most of the top of the door angle, really not an issue for me.

We picked barn doors for all sorts of reasons. loading/unloading, air conditioning, versatility, We add ramps for the few times we need to load wheeled stuff. In this case I can latch/and or lock the right side, and the left side is secured from the outside by the removable A/C box/closet.
Here's a few links to get your ideas narrowed down a little.
http://www.tnttt.com/viewtopic.php?f=42&t=65926#p1168566Our build, to help answer questions why/why not, and this vs. that...
http://www.tnttt.com/viewtopic.php?f=42&t=48345Window A/C discussions: Ours is in both posts below...this forum is almost too awesome. So much information, it's hard to sort through it all.
http://www.tnttt.com/viewtopic.php?f=42&t=50223#p932938http://www.tnttt.com/viewtopic.php?f=42&t=49438#p956281Last, have you talked to these folks in Colorado? They sell the brand that I bought, but made in the Texas plant, one of the few family owned manufacturers left, and even with a few hiccups on my custom build, I still think it was a lot of trailer for the money, and I'd to it again. ~ $ 4,600 delivered before my build. Price included windows, RV door, and e-track, extra vent, 4 stab jacks, and single step at RV door, mine was ordered through a local dealer and built in the Georgia plant. This dealer is an easy day and 1/2 from you, what's buying a trailer without a little adventure to go along with it?
http://www.coloradotrailersinc.com/2017-cargo-craft-6x12-off-road-cargo-trailer-new-cargo-trailer-co-i2049549Edit: sharp eyed readers, I ordered the Expedition model, nicer exterior features, then had them delete the 4" drop axles, and install the standard leaf spring axles from the cheaper Explorer model to get better ground clearance. They had a hard time understanding my logic on that one, but they did it!