To answer all the questions at once, No, the little obs can't be added to, resized, or have the door swing outwards.
About the only thing worth trying is Phils idea of cutting a bit off the bottom corner of the door.
As long as snakes don't find the hole and use the cubby as a nice home
A new, larger obs would be the best answer. Not only due to the door problem, but because the scope misses each wall by only 5mm as it slews around!!!!!!! With that small tolerance, it took me a while to centre the mount.