Okay, that makes sense. Problem is, I need to weed the garden while washing the car. Or feed the cat while weeding the garden while washing the car, then stop feeding the cat while still washing the car, and then start feeding the cat again while STILL washing the car and weeding the garden.
Or wash the garden while feeding the car and weeding the cat, even.
It does me no good for my brake light to come on whenever it feels like it. I need my brake light to turn on immediately upon pressing the brake, even if my turn signal is on, and I'd prefer to have the attention grabbing rapid flash sequence fire at the start of either light coming on.
I understand now (I think) how I can have my brake light be turned on or off depending on what it's previous state was, and I think I can do the same with the blinking pattern for the blinkers, but I would have to omit the initial rapid-flash sequence 
Which, if that is the case, I'll just chuck the whole Arduino idea and go back to the stock system.
Or am I being a completely infuriating ass and not understanding something here?