Palatal expanders widen the face as a result of widening the maxilla, could reverse forces be applied to narrow the maxilla and face?

Not in adults: Palatial expanders work in children because the palate is still two separate pieces. In mid-teens it solidifies into one solid bone and can no longer be expanded or reduced with out surgery. Thumb/pacifier sucking in young children can cause an abnormally narrow palate and are often the reason a palatal expander is needed to return the palate to normal size.

It is not possible: You and your orthodontist can discuss which appliance is best for your, but there is no appliance to narrow the maxilla or the face. The orthognatic surgery can be done for this purpose.