Unfortunatly I cant run the 2" above the 3 " I'm a bit shallow to get away with that. I'm working on another idea. Stay tuned!The U of the P-trap would not be under the wall. The trap arm would go to the wall, get vented, and then turn whichever way you want to go after being vented.
Use 3 inch instead of 4 inch to reduce height.
Instead, can you run the lavatory drain pipe over the 3-inch, join the shower trap arm with a wye (thereby wet-venting the shower). Then the output of that junction wyes into the 3 inch.