Summary

A single 9g servo may be too weak for steering. But there is a problem with the space for a standard servo. So what about two 9g servos? Two servo is even capable of DAS (introduced by Mercedes).

Use standard ball joints (see thing 3928619), upper and lower BOM are designed for standard ball bearing 3x6x2.5mm.

There should be enough space for the wires around the servos. Fix wires by hot-melt adhesive.

You will need transmitter with mixing capability. For precise wheel movement you will probably need define movement by 5+ point curve.
Thing 819938 can do it all. :)

Works great! With no correction (I was only set center and mechanical servo limits) the steering works approximately as single servo original.