1. That pipe you intend to hook the toilet to, is the vent for the first floor so you CANNOT do it.
2. Some codes allow 1/8" for 3" drains, although just as many require 1/4", and all codes require 1/4" for the smaller drains.
3. You might have to raise the floor about 8" to accomodate the required piping, and that would create a tripping/falling hazard, plusmight DECREASE the value of you home because it would probably turn off most potential buyers.
4. You might NOT have to damage the lower level ceiling, (once you figure out how to get a new drain line to the upstairs), depending on HOW you arrange the fixtures, and how the floor is constructed.