INTP:
Switch to an LED bulb of the same shape and your project is vastly simplified.
I realise that my bulb might be an incandescent one so it won't hurt as much as it was an halogen one.
I don't want to change my car lights, too expensive, less or more brightness and also not the OEM color of the lights
Either way i still need to build a high side switch because the lights are permanently connected to ground and switched from a relay on high side.
Edit:
I saw this video and i'm thinking of replicating it, since i got no other suggestions from here