With the wall side open, you could rout a conduit with FK so that you get a completely concealed installation. Difficulties may arise in the ceiling as the pipe outlet would need to be moved closer to the wall side.
The line going downward could also be placed in a conduit to make it concealed. However, it may be tricky with the transition to the surface-mounted cable, so you need to install a cable in the conduit up to the switch.
The cable type must not be EKRK if it is installed concealed. In that case, the cable must be changed to, for example, EXQ.
It will be difficult to make it look nice with the existing cables. Expect that they will need to be replaced no matter what you do.