Good idea. Yes, I believe that would work. I saw another random, non-rear reflector related YouTube video, where a guy installed one of those aftermarket sequential tail lights from AliExpress. The guy in that video ran across a similar issue with the turn signal when installing the Euro spec tail lights on his US spec Model 3. As a viable work-around/solution, he mentioned doing the same thing… taping into the front fender turn signal. Ultimately, he decided not to do it because it was too much of a hassle to find a good path through the vehicle and run the wiring from his tail lights to the front fender signals/harness.I was just thinking about this a little more and the idea hit me. Wonder if these would work fully if you unplug the Turn Signal harness and connect that yellow/blue combo wire to the existing wire running the fender side amber turn signal. The fender camera/Turn signal combo is a dedicated turn signal only, so maybe a quick wiretap and run some new wire inside the car tucked along the door sill trim back to the taillights, etc.
Just a thought. This way the Black/REd wire that powers the LED bumper lights will stay lit and a new separate source for signal would be coming from the fender blinker.