Yeah, I would think your idea is doable. You would just need to order a door for the outside. As long as there is nothing inside the wall where you want the door cut, it shouldn't be to hard to add one.
2013 Ram 2500, 6.7 CTD, CCLB 4x4 in True Blue.
B&W Turnover Ball, Andersen Ultimate Hitch (v2)
2016 Eagle HT 29.5 BHDS Picked-up 4/1/16
2007 Rockwood ROO 21SS - SOLD