On later Panda models (post 2015?), with front and rear fog lights fitted, the single switch is used to turn them both on: one press for front, and a second press for front and rear. Third press for ‘off’. (On pre-2015 cars, there were two separate switches.)
There will be no wiring ‘in the engine bay’ for this - it is all controlled from the ‘body computer’, that is integral with the fuse box inside the car. To have this be able to understand the one press/two press info from the dash switch will require it to be reprogrammed. The switches are only push buttons - they don't 'stay on' when pressed - it is the computer that does this. That also means they revert to 'off' when the ignition is turned off. Also, crucially, if the front fogs are turned on, it also turns on the rear tail lights, lights the dash and dims the radio, and switches off the daytime running lights and puts the side lights on -- there's a lot happens when that simple switch is pressed. The signal from the computer will be sent to the relay for the front fogs, which is probably in the second fuse box by the battery. There *may* be some existing wiring to the front fogs in the wiring loom, but I wouldn’t be surprised if there’s not.
There is also the issue of adjusting the beam height. The small hole in that plastic part beneath where the light goes lines up with the adjusters on the ‘real’ Fiat light. Will your non-Fiat lights’ adjusters line up with that?
