I had nearly the same situation with my tub vent. It ran up the middle of the wall, and I needed to get 1/2" copper past it horizontally. My plumber cut the vent pipe and installed two 22 1/2 degree elbows, pushing the vent toward one side of the space, then drilled out the stud at the opposite edge to run the pipes. He put nail plates over the pipes to insure that I didn't drive screws into the pipes...
The two elbows weren't perpendicular to the wall, but rather at an angle, so the vent pipe went sideways and backward if that makes any sense...
Unfortunately, I didn't get a picture of that section of the plumbing before I closed up the wall, so I made you a drawing. This is a cross section of the wall, showing how he moved the vent toward the right, and ran the two 1/2" pipes to the left.
Hack (a.k.a. Jeff)