Designing a small second story addition on my home. Can drain be run on the outside (boxed in) and under a porch?

[justinNY]

I am designing a second story addition to be built over an existing room. The goal is not to disturb the room (laundry room) since its been recently renovated. Its also framed with 2x4 walls (making it difficult to a 3" drain). The pictures in the link should describe what I am looking to do pretty well. Obviously this section would be uninsulated, but also not fully boxed in (under the porch).

I cant find a building code relating to this. Bonus points for feedback on the wet vent design.

https://imgur.com/J8ZJHgI

https://imgur.com/AQvZi1Q