I am in the process of remodeling my bathroom, and when I opened a wall to incorporate the closet on the other side, I found the house's main vent stack. It goes from the basement to the roof and services all the house's plumbing. It is a 5 or 6 inch cast iron pipe, with a few connection in the wall to be taken out. My question is, can I cut this pipe just below the floor and top it with a Tee then route it over a few feet left and right, then up the exterior and interior walls of the house, then back to the original exit in the ceiling. I would be splitting the pipe into two section to facilitate the venting of a shower and sink on the interior side, and a toilet and the vent pipe from the bathroom below. All the new pipes would 4" ABS.