Looking at the picture,
I'm not quite sure why the trap is turned to the side instead of going straight back?
The Santee is existing and already at a set angle, so he has to accommodate what he has.
Yeah, he can blow out more concrete.
Dig down to find the santee sitting on top of a combo, fitting to fitting.
Move the wall studs so he can work on the vent above the floor.
( Why R the 2 studs so close to the vent like bread on a sandwich? )
is it because the trap arm would be too short? I believe the rule is that the trap arm has to be at least 2 pipe diameters. Would it meet that requirement if it just went straight back and connected to the vent? If so, then you could turn the trap facing straight back, have a short straight trap arm, and connect to the vent / drain with a sanitary tee. I'm assuming that the vent pipe goes down further underneath?
I suck with visualizing dimensions, so I don't know if you can get 2 pipe diameters between the end of the trap and the vent pipe. To my eye, it looks like you can get the 2 pipe diameters, but I could be wrong.