There are a few problems with the current way the game does wing mirroring. Same input surfaces such as elevator control (pitch) or flaps do not work well with mirroring. In order to achieve these, wings currently need to be constructed in segments and/or be non-mirrored.
More types of control surfaces such as non-hinged, leading-edge flaps (slats) and speed-brakes would also be a great addition, and less critical but also great would be the addition of different types of flaps in addition to the hinged-type we can have at the moment.
@Kell I know. The issues described above occur even when using invert.