Move drain in cellar to wall above it

[James23912]

I am looking at a carpentry job for a neighbor, she wants to make a finished room in her cellar and move the washer upstairs, she would like to have as flat a ceiling as possible. the main drain runs alongside the foundation so that can be boxed in but there is 1 1/2"another line running about 5 feet into it that has 1st and 2nd floor sinks and would have to be enlarged for the washer and the joists run the wrong way. There is a 3" toilet drain from second floor near the outside wall that drops directly into the cellar drain, and it is a 2x6 wall , she will get a plumber but I am wondering if there is any reason that the smaller drains cannot be run on the first floor wall thru the 2x6s and into the vertical 3" drain from upstairs. The wall in the new closet for the washer set up could be left open at the bottom and if needed she would be okay with a small access panel in the kitchen that would allow for a cleanout in the new set up.
it would basically be the same as what is now in the cellar, only on the first floor wall