The Grand Wazoo
Using a vent as a waste is a code violation here.
It's only roughed in as a vent line right now. I would be using the line that is supposed to be the vent as my drain line and then use what is supposed to be the drain line for my vent. So the drain line and vent line will be independent of each other, but basically wantng to know if the two can be swapped. It seems to me that I could use it this way, but really don't know the design practices in plumbing. This vent line also vents the bathtub and toilet.
This.Using a vent as a waste is a code violation here.