I'm working on a turn of the century foursquare style house. I want to put a bathroom in a room directly above the room where the existing bathroom is located downstairs. There's even a 4" pipe running up through the room and out the ceiling. I'm assuming that this is the air vent on the sewer line in the bathroom directly below. If confirmed, I also assume I can tee into this from my new upstairs toilet. I also want to add a shower and vanity.

I can line the toilet up with the existing pipe so I'm between the same floor joists but for the shower and vanity, I was planning on drilling 2.5" holes through the floor joists and meet up with the toilet drain.

Can you shoot holes in this plan?

This room is a total demolish and remodel so it won't be a big issue pulling up the tongue and groove. I'd like to keep it if I could but it's not mandatory.