A SIC is always required under IFR under 135. An authorization is required to fly with autopilot in lieu of a SIC, but not to fly with an SIC, as that's already a regulatory requirement. An operator may hold authorization to fly single pilot with autopilot, but is not required to do so. An operator to whom is issued A015 is not required to operate single pilot with an autopilot, and may operate with a SIC, if the company has a SIC program and a SIC-qualified pilot is available.

No additional authorization or special dispensation or operations specification is required to follow the requirement of the FAR, which is a SIC for operations under IFR.

There is no operations specification, or authorization, for the FAA to withdraw, which permits the operator to use the SIC, and there is no authorization to use a SIC in lieu of an autopilot. No authorization needed, or given, and no such OpSpec to withdraw, as the base regulation always requires the SIC. It's the authorization to operate single pilot with autopilot in lieu of an SIC, that the FAA can withdraw. Not the other way around.

We've established that quite clearly, with links, at this point.