I posted a similar diagram yesterday, but said I don't think a flash would be discernible because: using the diagram you added diodes to of Jerry's, it is my guess that while brake is applied in the turn, when the transition happens as 87a and 87 latch back and forth, which is an ON/ON in a split sec, that the filament which is brake and turn will look like it's not flashing. Experiment will tell. I decided not to pursue that diagram I posted. Jerry may have used this method and knows it works. I could be paranoid. I prefer intuitive.

Also where would the "feedback" be coming from to the brake wire? Why diodes there?

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn