If I have a charge of +q placed arbitrarily within the spherical conducting shell, by Gauss' law, the E field produced will be created outside the shell, as if the charge were placed at the center.
That isn't a law of physics. In fact, it only happens when the spherical conducting shell is electrically neutral.
Here's what happens:
Based on the charge inside some opposite charge arranges itself on the inside of the shell to shield the shell (and all the space outside) from the electric field due to the charge.
If the shell had a charge equal and opposite to the charge inside and there aren't any charges outside that would be it, there would be no electric field anywhere in the universe except on that inside surface and the charge inside. Laws of physics satisfied.
Now if there is some charge outside and there is +q charge on the outside that is free to move around, then the charge arranges itself on the outside of the shell to shield the entire inside (shell and the cavity inside) from the charge outside (just as if the shell were a solid conducting ball).
Now. What if the shell had some charge (possibly zero, but something fixed) and wasn't connected to a source of charge. Then every bit of charge that appeared on the inside shell or the outside shell needs to be added up and compare to the total charge. So if you have -q on the inside surface and +q on the outside surface you get a total charge of 0. But all you needed is that the inner surface needs to be -q and the two need to add up to the total charge.
Now. What happens if the charge inside is put somewhere else. The field on the inside surface will be the same magnitude but will be rearranged differently. But the two together produce a zero field outside. The charge on the outside surface doesn't change and that's what makes a field outside.