I'm finally picking up what you're putting down. I think it WOULD be way easier this way. I hadn't even thought about doing it this way. This is why I wanted to try and "noodle" it out on here before I got too carried away.
Building is sitting in the yard. I don't remember what we came up with on the snow load. I don't THINK that with a 4:12, we are going to have much sitting on the roof though.
It looks like that in 2D. From 1st to 2nd, there is a landing and a turn to 1 step.If you look close in the picture, it shows a SHORT railing by the open area for the 1 step.
1) Outside rim board, I bet I could weld a clip to the column to hold it.
2) Stairs I think should have 6'-7' right at the middle there.
3) I think I like false ceiling best.
4) I don't think any welding or exhaust that will happen will be for a long enough time frame to bother the "house"...