Well, you can change the "signal_R" and "signal_L" functions to just "brakelight_signal_R" and "brakelight_signal_L" just like what we have on the Bastion, so when braking, the signal from that side will overcome the brake light, so it will flash even with the brakes pressed. Just like what happens on the front, between the DRLs and the front turn signals. When you signal left, for example, the left front DRL starts flashing, even with the lights on. On the rear the same should happen with the brake lights.
Just taxing around russian province town) --- Post updated --- I noticed that the car does not have a petrol cap
Yep. I could even make the light props work. Although the light texture is still the same since I couldn't change that. Since you have all the files, maybe you can make the visuals work.