I used to have a pop hole door that was hinged on the bottom. The only reason we replaced it is because we changed to an automatic door that slides up and down.
It opened to the inside, so I could use a simple latch and still keep the raccoons out. I didn't want to have to fumble with locks outside, when it was -20 and getting dark. Since it was a hinged door, it adapted to the level of the deep litter.
On the outside, we've always had a stationary ramp, since the door is on the inside.
Although some people have had trouble with their chickens standing on the ramp and pooping on it, that was never a problem with our chickens. I think that's because my pop hole door was higher up in the wall, because the coop was designed for deep litter. The ramp was steeper than others I've seen and that makes the chickens less inclined to want to stand around on it. They just move along. Plus, mine can always look out the windows if they want to look outside, without going outside.