It would be great to have a "passenger" icon like :
I have seen these icons. But for me, icons look like driver icon and not passenger icon.
Removing the steering wheel arm looks like the change needed for this.
I think it'll look weird without the arms or with the arms laying down to the side.
In context I think it might be fine. Lets get some design ideas for this first.
I agree with @MrGrigri, this provide no new meaning over the existing version.
I think in context with a diagram showing top down seats this will make more sense in a vehicle.