Yes to the plumbing part. You must keep the pipe that goes to the sink tee 2" to be a legal wet vent. Even if you could keep the 3" for the toilet jammed into the joist space I doubt I'd want to drill 2 3/4" holes through the joists for the sink drain pipe. Head to the DIY carpentry for that stuff though. Good luck!
thanks again. please see attached pic, i know its rough, but hopefully workable. So i'm using a sanitee 3x3x2 where it enters 2nd floor, and then a wye for sink and tub, any special kind needed? Then a regular 90 at the toilet? And for the 1st floor sink, i don't have access behind that and there is a large window above it across kitchen. Is there any other way to vent that? Thanks